Google, similarly, will be killed not by a competitor rising out of nowhere, but by falling into irrelevance.

Be careful. What's the quote? "It's difficult to make predictions, especially about the future." People said the same of Yahoo in the late 1990's. It had many competitors but wasn't really challenged for the top spot. Google came out of nowhere and relegated its dominance of search.

"Facebook, on the other hand, doesn't have any such flaws." ... "Facebook is as unkillable as Google." ... "You won 't kill Facebook. No one will."

Facebook and Google usurped their predecessors from out of nowhere. They both wouldn't exist if their founders said to themselves, "I'm not going to try to overtake Yahoo/MySpace -- they're unkillable." Your flimsy advice is now recorded to be ridiculed later because you seem not to understand the very nature of technology.

The next leaders get this sort of insipid advice all the time but, luckily for all of us, they aren't listening.

Facebook and Google usurped their predecessors from out of nowhere. They both wouldn't exist if their founders said to themselves, "I'm not going to try to overtake Yahoo/MySpace -- they're unkillable."

I think Facebook and Google did exactly that. Facebook was just another "me-too" social networking site at first, targeted at a limited audience; I doubt that right from the start they thought they could be the #1 site on the internet, or even the #1 social site. And AFAICT, Google's initial goal was to provide a better search, not to supplant all other search engines.

In fact, in my opinion, what they have in common is that they both didn't aim for the top at first; rather, they carved out a niche, then worked from there.

That's a little uncharitable. I joined Facebook fairly early on (when it first launched for college students), and it was the first social networking app of any sort to even hold my attention. Friendster came and went without me ever visiting, so did MySpace... We may not like all that FB is doing, but IMHO it was a lot more than a me-too, even in the beginning.

Turns out, those "features" weren't actually good things. And when MySpace turned into a spam infested, buggy, always down piece of crap we all turned to Facebook. Honestly I think Facebook blew up in that time because MySpace dropped the ball. I don't remember anything compelling about Facebook at the time when the bulk of my group switched, other than that it didn't break so much.

Yes, but lots of people wanted to be like Yahoo. I think the whole portal idea came from sites wanting to be like them.

We seem to overestimate change in the short run and underestimate it in the long.

But you can't quit your friends. Social networking is a winner take all. That is why i agree with the author that Facebook would have to shoot itself in the foot first.

My friend, for your sake I hope you never have to fully understand what I am about to say...

But there are times when you not only will quit your friend, boyfriend, girlfriend, husband or wife, but you will have to.

You can quit your family too.

When I was twenty I had no comprehension of this, but having almost reached forty I can reel off examples. Most of which are not mine, fortunately, but some of which are so painful that they hurt even by proxy. Mental illness. Divorce. Physical abuse. Emotional abuse.

Facebook, by the way, with its ridiculously naive conception of identity and privacy, is actually a lousy platform for conducting real-world relationships. It's like trying to compose a story out of the messages written on greeting cards.

[Conducting relationships on Facebook is] like trying to compose a story out of the messages written on greeting cards.

Insightful. Hilarious. Wow.

It might have been. Deliberate, experimental misinterpretation is an important essay-writing technique.

Part of the goal of essays is to arrive at new thoughts. To get to someplace new you have to try some wrong turns.

If you can't think of anything novel, write down the obvious. Then try deliberately misinterpreting what you just wrote. It's usually painfully easy to do.

"Conducting relationships" is a multi-faceted concept in my opinion. It involves several layers of communication and Facebook is just one of those, not THE only one.

Let me give you a concrete example of how Facebook has helped me conduct a relationship that I find rather meaningful in my life. I have an American friend living in Switzerland of who I've met some good friends of his. One is a British guy who just recently moved to Dubai from Switzerland for a short term project. Had it not been for Facebook I probably wouldn't have known he moved there and thus provoked me to book a trip to see him several weeks ago. (another form communication - physical presence) He's only there for a few more months and I'm afraid any other form of communication would have been too slow.

Sorry to de-rail your original point but I always find the "Facebook haters" to be rather interesting. And to you're original point about quitting friends. I don't think he/she meant literally that you can't quit all of your friends. The point is that you will always have a social network of people in your life, whether you continually add or delete people. If you don't (and I would feel exceptionally bad for you) then you represent an extremely small percentage of the world's population.

Sure, but that doesn't mean that Facebook will stay in business, let alone stay fashionable or popular. People have a choice between eating and death, but that doesn't mean that McDonalds will stay in business until humanity is extinct. Though they obviously have quite a headstart in fast food and are doing very well.

The other interesting word in this excerpt is "a". People have "a" social network in Facebook, but they have way, way more than "a" social network in real life. We each have hundreds of overlapping social networks, some with precisely defined membership, temporal, and physical boundaries (I'm not polygamous, so my marriage social network is strictly limited to two) and some with extremely fuzzy boundaries (HN).

Facebook has gotten ahead because, though it offers one particular style of social network, it makes it so very, very easy to use that network -- and it has such a great viral loop and name recognition --- that for the moment it is tempting to pretend that all of your hundreds of real-world social nets can be collapsed into one. But the web is a big place, the future is a long time, and UX innovation can and will be copied.

Absolutely agreed. I was raising questions about the point for the absolute existence of a social network. I think what the originator of this discussion was saying is that any social network is a necessity to living (much like food and shelter). In other words there will always be a market for such a platform (as opposed to say something like selling iPods)

Also I'm interested in understanding why you think Facebook's concept of identity and privacy is naive? My identity is composed of the things I like and my privacy consists of the things that I like that I wish to share with people. Facebook gives me every opportunity to do exactly both in an extremely controlled manner.

It doesn't even have to be that dramatic. People change and drift apart. The older you get, the more extreme the examples become. I often forget the names of people I once considered friends for life.

The more they pile up, the more Facebook changes from keeping in touch to unwilling voyeurism. The FB killer will be something that deftly handles change.

However, Facebook has some things going for it that ICQ didn't. for example:

Grandmothers - Facebook started with the early adopters just like everyone else. But they slowly moved (and are still moving) down the curve, past the 'what's a browser' middle and down to the users for whom email is a big challenge. People who basically don't use computers except for occasional tasks that someone else has shown them how to do and set everything up. These people don't switch easily.

My fiancée and I are in our late 20s. We were in college when Facebook came out and arrived at the party early. We built our social networks to share the fruits of our newfound "adult" freedoms- namely pictures of inappropriate Halloween costumes and drinking games.

Now, Facebook is different. My mom is on it. My mother-in-law-to-be is on it. But because my fiancée and I are on it, our children likely won't be. It won't be a fun place to share things you don't want mom to know. Mom will be checking in and leaving embarrassing messages on your wall. I think my kids will probably find somewhere else to hang out. It will probably have a name I can't seem to remember, and I will likely embarrass them in front of their friends by pronouncing it wrong or misunderstanding its key features.

Social networks are binding, but they're highly generational. Unless Facebook can figure out how to get my future kids to think its cool, it's toast in 20 years or less.

--Edited for grammar--

Already I see awkward parent/child relationships. To the parent, they love feeling 'in touch'. To the child, it's just embarassing that their parents are hanging around on Facebook. As they move into the embarrassing photos/stories, they're either going to find a new platform or create a separate identity, or something, to conduct themselves online in private.

SMS was the killer app for teens because they could exchange messages with friends (a) cheaply and (b) without being overheard.

What's going to kill Facebook is something better. Less spam, better privacy, etc, but it still needs to be at least as good as Facebook to get anywhere. And that’s going to take a seriously long runway a great development team and awesome management. Look for a profitable nitch like LinkedIn that just keeps growing.

Grandmothers won't save Facebook. They'll allow Facebook to linger on like a maladapted dinosaur or the old VAX your IT department uses as shelf space. But in a post-Facebook world, just because we all keep Facebook accounts to maintain ossified relationships doesn't mean Zuck still has social relevance.

If I found a new social network that I thought offered something new I would start using that in parallel to facebook. Then I'd use the new one more as more people moved over, until eventually facebook just became a way of emailing my grandma.

A lot of these facebook killer conversations seem to be based on the idea that I'm only going to use one social network. I'd argue that's not true at all.

In technology, the word never is a fool's word.

Obviously sms still has it's place (ie- want a response in the next 10 minutes rather than the next 24 hours) and nothing can replace in-person communication -- but FB is doing a damn good job of replacing my electronic communication.

You can quit facebook if there was a better way to connect to your friends.

Google beat Yahoo at their own game.

Facebook beat MySpace at thier own game. It's a different game than Google were playing, but Facebook made their game more important than Google's.

Google has something like 30x facebook's revenue, and is still growing at a tremendous rate. Facebook has been growing faster but it'd be silly to imagine that their several hundred percent growth rate could continue forever. Worse yet, facebook's per user revenue is so poor that if we were to assume that their user base expanded to include every computer owner in the world they would still not match google's current revenue.

Facebook gets a lot of exuberant press these days but make no mistake, they still have many huge challenges ahead of them. Even if facebook were to double its revenues every year it would still take 4-5 years to catch up to google. A lot can happen in that time.

The first is that it is built from the ground up around a flat social network and that maps really poorly onto real social networks. Sure they can add things like groups to try and address this but it's baked into the DNA of the site and the way people think about the site. The blog post that accompanied the recent profile refresh really brought home how they do not understand this. Listing work projects and who you worked on them with on a friend-oriented service? Promoting parts of your life so more 'friends' can learn about them? Who on earth wants to do this stuff?

The second, which is part of the reason for the first (college social networks are relatively speaking flat) is that Facebook was built and initially populated by the Ivy League. It was the classy, exclusive social network. Now it's everybody's, there's like buttons on every site, every brand from downmarket crap to luxury. Every market has price differentiation, social networks will be no different, there is a huge opportunity for a more exclusive, more upmarket network and when those users bail on Facebook there's a real chance it'll cause a cascade.

This flaw is obvious enough that it inspired an SNL parody ("Damn It, My Mom Is On Facebook Filter"):

http://www.youtube.com/watch?v=t0Bd9-xOQjU

It's pretty funny, and its appeal isn't limited to geeks.

It will be astonishing if that does not happen, at least in America. If there is one consistent factor in American culture, it is that your kids will find something to do that is superficially different from what you did. They don't dance to their grandmother's music - except as retro kitsch - and they won't use her social network either.

Alterna-Facebook may be almost exactly like Facebook, it might be compatible with Facebook and it might even be built and run by Zuckerberg, but it won't look like Facebook and it won't be branded as Facebook.

Facebook itself will not die, of course. But it might just settle into its niche. Consider a related - but more primitive - example of a niche genre: high school yearbooks. They are a steady, stable, hundred-year-old tradition but they never grew to threaten, say, newsmagazines, or scientific journals. They are what they are. They are just one genre. Everyone has one, and for a couple years in everyone's life it might even seem important.

I read somewhere that a few years ago, their staff were walking around wearing t-shirts emblazoned with "Your Mom has a Facebook Page". The article was about how they were trying to position themselves as a more youthful, 'alternative' social network.

Don't think it really worked, though there's certainly still a lot of bands on there. Besides, if some upstart did recast themselves as young and hip and Facebook as old and fuddy-duddy, Facebook could reframe themselves as classic and sophisticated (similar to the changing brands of Pepsi and Coca-Cola).

As people get better at, and better tools for, segmenting their lives on FB, I don't see why FB couldn't persist.

Exclusive maybe, I'd stop short of referring to Ivy League students as classy ;-)

Also, I like how both of the exclusive networks for the rich mentioned in sibling comments apparently couldn't afford a .com domain name :)

http://www.affluence.org/

http://www.asmallworld.net

I still haven't received an invite:)

Me either.. but if somebody has an invite available... well... my email address is in my profile. :-)

A) You need to accumulate lots of data to even have a chance to beat Google. No algorithm you come up with will be competitive until you have a mound of data similar to theirs, and accumulating that data takes years.

B) My friends leaving Google has little impact on me. So, with a Facebook, you can pick off a city or social group, and snowball that. That's exactly what Facebook did to MySpace, and there's no analog in beating Google.

To beat Google, you need time, money, and it's a moving target. That's why the only serious contender is Bing. To beat Facebook, you need a better design, indomitable passion, and clever marketing. Really clever marketing.

What is keeping you on Facebook is just the fact that they have your list of friends and family. I'm not saying Facebook is easy to beat, and I believe over time, they have accumulated some of the defenses that Google has. However, a company built on a network effect can die by a network effect. Easy come, easy go.

If you must create a social network to compete with Facebook, make it be a part of Facebook at first too. Integrate it. Make sure that it takes me zero effort to jump between Facebook and your Smashbook. Then start improving your Smashbook in ways that Facebook cannot or will not. Add those better privacy controls. Implement a better social model. Remove annoying ads. Basically, do what Gmail did to Hotmail: it uses the same system and I am not cut off from my friends if I switch, but I get to use better tools. But there is no way in hell that you can start a social network about collecting stamps and gradually outgrow Facebook. You may make a decent chunk of change on this, so it may be worthwhile, but it will not kill Facebook.

For example, now when I am searching for news, like I want to know what's new with wikileaks, I start my search on twitter, where I get more fresh and more diverse info. Or if I want to know about something I know very little about, I start on Wikipedia, etc.

So while Google can be unkillable, other companies can make it less indispensable by providing completely new ways of searching for info.

I think there is a vector there that could be used against google.

verticals.

There are several social aspects of our lives that are very poorly served by Facebook and that's where verticals will come in.

Verticals won't necessarily kill Facebook, but they have the potential to chip away at the centralization of data inside of the Facebook social graph itself.

Under this scenario Facebook would still act as an aggregator, but then again the barrier to entry for competing aggregators of social network verticals would fall substantially and allow innovation and specialization.

I know of at least one stealth startup working on such a vertical, but I can't mention who just quite yet. From the ideas I've heard, the potential is definitely there in the idea to corner one aspect of a users life that Facebook couldn't possibly match due to the high level of abstraction FB needs to maintain as a generic social networking site.

I think verticals could also erode Google as well. Quora is going after one aspect of knowledge. Wikipedia as well.

If I were to create a search engine today, I'd go after one vertical. For example, a search engine focused entirely on helping you find code would be immensely valuable. Sites like Github and Freshmeat have search, but the search isn't specialized to add any value over what Google already offers. In fact, in many cases sites with specialized knowledge about one vertical choose to use Google's search for its own site instead of building a new search from scratch that better serves the need of that vertical.

Examples of verticals where I see value in creating a specialized social network or search engine:

-- Nightlife

-- Code/Programming

-- Educational resources.

Nightlife? Sure, but once you have a favorite club or 2 where you hang out with friends regularly, you don't need a website to tell where to go anymore.

Educational resources? You mean like lots of scanned books that you can search?

What will make Google irrelevant is a better search engine: just the other day I remembered a piece of article I first read a couple of years ago. It's somewhere out there but I can't find it because of all the junk and all I remember are a couple of words and a number.

In 2002 when I first used Google's search, I had been using Altavista previously. The results from Google were so good compared to Altavista that it wasn't even funny. If the same would happen today, Google would be in big trouble.

Also Facebook is already irrelevant to me. I log in from time to time, responding to a friendship request, but these days I only view it as a tool with which I could spam my acquaintances in case I need it :)

That's a pretty funny comment here on HN -- a vertical

The truth is that people spend most of their time in verticals.

Statistics focus on the aggregate amount of time the average American spends on Facebook, 7 hours per month.

But the truth is that what is most interesting is the 20-40 hours a month someone spends on the verticals that matter most to them.

For us it's nerd/tech stuff, so we hang out here for hours on end. The number of hours I spend on here blows the amount of time I spend on Facebook away. The same goes for Quora.

For companies that make money from advertising, the highest click-through-rates come from the most engaged audiences and highly targeted advertising.

The truth is that no one has perfected many verticals. StackOverflow is one of the the best examples of startups that have done an excellent job in a vertical, but there is still much more potential there too.

Regarding search verticals, the search algorithms for code are going to look really really different when compared to those for natural language that Google is after.

Imagine a code search engine where I can save preferences for the languages I want to search in. This engine then indexes lots of different places like Github, Gitorious, Freshmeat, SourceForge, etc.

If you are part of the community that cares about code, you all of a sudden stop going to Google as the default for all code searches. Of course, Google could then become a portal to your search, but at that point the the barriers to entry for other companies to aggregate vertical search engines becomes much lower and Google's dominance is no longer guaranteed.

So, what will "kill" Facebook? It's simple. What will kill Facebook will be its own stupid users.

“Just think of how stupid the average person is, and then realize half of them are even stupider!” - George Carlin

Firstly, facebook's technology advantage will evaporate, especially as hardware improves. The cost of serving facebook's traffic and of managing the infrastructure to serve that traffic will come down over time until ultimately it's as abundant and cheap as a linux VPS is today. Somewhere along that trend you'll see an explosion in very capable facebook competitors. People as savvy as Apple and as technologically competent as google. Ultimately I think the result will be fragmentation and loosely federated disjoint services (much like email is today).

Secondly, facebook will one day become un-cool. When your parents' generation and your grand parents' generation move into your social media platform en masse that can change its nature. Eventually facebook's allure will fade, and perhaps some new thing will draw the attention of the younger generation as it always has.

Thirdly, facebook has a pretty sloppy business plan. Their core idea has always been "grow big first, figure out how to monetize that second". The downside of this is that if their growth stalls or they shrink then they are left high and dry with no revenue and no wealth to try to turn things around (see digg, myspace, etc.) More sophisticated competitors with more robust business plans from the get go have a chance to take facebook to the cleaners. I competing social media platform able to be far more efficient in terms of revenue generation would be a serious threat to facebook.

The same thing will happen to Facebook as happened to AOL. It will exist for years to come, but it will be forced to open it's walls, and play nice with an open standard. Younger users will leave for more niche communities which interconnect, and older users will stay with what they're used to.

In other words, in 5 years, Facebook will be for old people. As well as other people who prefer familiarity.

The history of the internet is a history of decentralization winning over walled gardens. There are too many projects pushing for decentralized protocols and solutions. Appleseed, GNU Social, OneSocialWeb, etc. I think the last time I checked the spreadsheet, there was over 50 such projects. Some of us are pretty close to providing a viable alternative, too.

But most importantly, we're not going to give up. No matter how much people may think of Facebook as infallible, we're never going to throw up our arms and say "oh well, I guess we can't win". We're going to keep pushing and refining our solutions and building momentum until we win.

The Next Big Social Network tm may even run our software on the back end, and people will move to a distributed system without even realizing it.

Facebook is odd in that it improves on a previous solution (communication tools: mail, phone, cellphones), but doesn't charge for the utility it brings.

All the other companies won because of their products, for whatever reason -- usefulness, ubiquity, etc. If someone came up with a product that had better usefulness, ubiquity, etc. then users could leave.

Google leveraged network effects with publishers. A search engine to rule them all. It had publishers by the proverbial "balls" -- if they didn't play nice, Google could just delist them and they'd lose their main source of traffic.

But the users were always free. Free to switch to yahoo, or bing, at the drop of a hat if they liked their search engines better.

Facebook is the first company I know that has successfully pulled off the following: it has its own USERS by the balls.

If you don't like facebook, you can bitch about it and even delete your facebook account, as various random people claim. And then a couple months later your friends want to share their X (pictures, notes, etc.) with you and not EVERYONE IN THE WORLD. And to do that, you have to join facebook again. Yes, facebook, because joining some other site will do no good.

This works because leaving facebook is no longer as easy as making a personal choice. You now have to create more work for all your "friends" who are sharing stuff with you on facebook.

"Larry, didn't you hear? I got married! Everyone came to my engagement party! It was all over facebook"

"Sorry baby, I'm not on facebook anymore... I guess I'm out of the loop"

This is a new ball game. Of course, facebook also has PUBLISHERS by the balls, just like Google, since it drives lots of traffic to them.

But it's the first company to have users by the balls. So what if you delete your account? You are in a tiny minority. And chances are, half of you will be right back on there the minute your friends refuse to share with you anywhere else.

So I would be a pretty lousy friend if I just notified people within facebook and ignored my other friends.

For many, Facebook solves a unique problem - it provides them with tools to help them manage their various relationships. It's ubiquity is a key part of its solution, and any other platform that wanted to supplant Facebook is obviously going to find it difficult.

Having said that, I think it's perfectly reasonable to think about what will replace Facebook.

As a company becomes larger - it will usually become less nimble. Unforeseen changes in the market's landscape, provide opportunities for new entrants - where the larger Goliath companies aren't as able (or willing) to adapt.

Facebook will be killed (replaced / supplanted) .. but without the benefit of hindsight, it's very difficult to know which company will succeed.

Why is it that when you buy a phone now it comes with Facebook (and twitter and google)? And, on many plans it's "free" to use Facebook and twitter, and you can't remove it. It's all about the channel. Facebook/Google/Twitter + ISP/Phone Provider = secure advertising channel. Can you turn off your radio? Can you turn off your TV? Can you use a plain old cellphone that just dials a number? The only way to kill Facebook is to turn off the advertising channel.

As an aside, the author feels that Microsoft tried to kill itself with all the delays and bugs in Vista, which I would also disagree with. Google, along with a host of other companies, killed Microsoft - because of the talent drain. Once your best and brightest are jumping ship for, as Michael Lewis would call it, the "new new thing", you are pretty much screwed because your product development is going to start going down the tubes.

That means, to me, that there is a really solid and significant world outside of Facebook.

From the end of the third paragraph in the post.

Nonetheless, the only thing that could probably kill Facebook is when people stop using it. Simple as that.

The whole thing was just manufactured by angry computerworld journo's who couldn't believe that MS actually started considering making an OS easier to use.

No one can kill Google except Google.

No one can kill Facebook except Facebook. Many people don't trust Facebook. That's a problem.

P.S. Thanks for posting a specific query. 90% of the complaints I see like this never mention a specific query, which kills me because I want to dig into it. :)

Err? You should check again, acronis.com ranks #1 #2 and #3 for "acronis true image", acronis true image, acronis and "true image" as well.

Wild divergence from actual search results sounds like local malicious activity.

The 5th - to the wikipedia page about the product.

"What will be the next giant wave?"

Great conclusion.

Don't underestimate the value of a good question; and don't expect every informative article to spoon feed the reader the answers.

This can kill any company.

Supposing the answer is "yes", I'd say FB flaws matter a lot. Even flaws that users don't see now as such, maybe because they see them as unavoidable. What if a new service, based on another model, arised and it hadn't such flaws?

There'll always be overlap when a competing platform comes into the picture - so any 'death' will necessarily be drawn out.

I like your wave analogy, because it highlights the way that these service-orientated companies are tied to the current socio-economic landscape. This helps to show how competition between companies isn't the most important factor. A change in market conditions can prove just as disastrous (as a good competitor) for a company like Facebook, and this kind of change is probably more likely to signal its demise, because a market-leader's success tends to increase exponentially when conditions stay the same.

I think the most interesting question is; what change would be necessary for people to migrate from Facebook to another platform?

It will happen - but when and how?

The weak point of Facebook is that it lumps everybody into the same "friends" pool. This is not a new observation of course, but is is still a problem, and Facebook hasn't really done much to alleviate it. Sure, you can add people to different groups, set different filters, but for most people (especially those who are less tech-savvy) this is just too much work (or too difficult, even). So the problem remains, and as Facebook gets bigger, so does the problem.

I think that at some point, there will be huge opportunities for "spin-off" sites, that address some kind of niche. There would be a mini-social network were you talk to your family. Another one for friends (of the kind that you go to bars with, for example). One for networking. One for co-workers. Ones for specific games (quite a few people on Facebook have thousands of "friends", most of which they don't really know, but were added for the benefit of playing Mafia Wars, Farmville, etc). And so on.

Some of these already exist, like LinkedIn; and likely, the process is already underway. However, I think such sites would have more success if they were friendly with Facebook in some form or another; log in with your Facebook account, maybe share certain things, etc. (Look at Zynga; would their games have anywhere near the current number of users if they had not integrated with Facebook?)

When you meet new people, online or in real life, in whatever situation, the common denominator would be that they all have Facebook. (Still going by the assumption here that Facebook would get so big that people without an account would be rare.) So it would retain its function as a "hub" where you can find anybody at all; but the actual social interaction, in whatever form, would be done at the spin-off sites. You don't post work-related things to your Facebook because nobody cares but your co-workers. If you had a wild night out, you don't post pictures of it to a specific site, not to Facebook where your mom/kids/spouse/boss can see it. For those things, there would be the aforementioned specialized sites. Likely, it wouldn't be long before we would think of such a situation as normal; you won't post specialized info on Facebook, any more than you would post it in the newspaper.

I am just brainstorming here, but if that would actually happen, Facebook would slowly be supplanted by a myriad of smaller sites, each with their own purpose. Facebook itself would slowly become irrelevant other than as a hub to connect all those specialized sites. Like Microsoft nowadays, it would be big, bulky, probably rich, but it would just kinda sit there; the action and innovation would happen elsewhere.

tl;dr: Hypothetically, there might not be one Facebook killer, rather, it might be replaced by many smaller, specialized sites.

Look at how IE is struggling against Chrome and Firefox. A few years ago Microsoft was in the comfort zone in terms of market share. Things began to stagnate. Now they are being pushed. They know they have to innovate, or face the possibility of fading away.

It's not a question of what will kill Facebook. It's a question of when.

Sure, every company gets more vulnerable as it gets bigger and markets evolve, etc. as stated here. but if you notice, NONE of the examples cited above "became vulnerable" before the liquidity event happened.

I could make an exception with Apple, but that seems to be the exception not the rule. in fact, you could argue that there is a 3rd phase of a company (which Apple is in), after the liquidity event, after the company gets vulnerable (think apple 10 years ago, think yahoo now). some die - but some survive to see a new healthy dominance.