I'm surprised that this comment was downvoted so much. I actually work at Google. I don't know if anyone is still going to read this, but I thought I would comment just in case.
I said "for the most part". There are multiple reasons why different users can see different ads:
Ads might be geo targeted ("Only show this to users in New York.").
There is some stochasticity in the serving process. Ads can run out of budget. Different data centers might have cached different things in cache.
Different advertisers that are eligible to show for a certain query can bid different amounts depending on the user, for example though RLSA [1].
But anyway ads personalization is not essential to Google's business model (except display ads and maybe youtube ads).
I like how you say "personalised ads are now essential aside all those times it is". The fact remains, personalised ads is always going to be far more profitable than non-personalised ads. You don't need to be an insider in Google to understand this. Moreover Google didn't even invent the concept of personalised adverts to begin with.
I'm old enough to remember when we had the same arguements about supermarket loyalty cards which track your purchases and sends out personalised deals. Now people just accept that happens but there was a massive uproar about it back in the 80s or 90s (I forget precisely when but it was a good few years ago now).
I honestly don't blame Google for doing what they're doing. It makes perfect business sense. What I do object to is Google employees (assuming you are who you say you are) trying to argue that Google don't make a business from personalised ads when it's pretty easy to prove they do and nearly every single member of HN has observed that it action. For the record, I also object to people argue who "X is definitely not y" while acknowledging that there are a whole plethora of examples where their arguement isn't completely factually accurate - that kind of dumb get out clause is just insult on everyone's intelligence.
