So true - a lot of people (me included) thought a billion dollars for Instagram seemed insane at the time. But it was possibly the deal of the century.
At least in the case of instagram you didnt need hindsight to know it was a good deal. Lots of people thought they price they paid was incredible value on the day it was announced. Plenty of ink has been spilled that year about facebook potentially being in trouble with mobile and instagram seemed at the time to be an obvious solution to the problem.
That is not my recollection whatsoever. A quick read through the HN reactions that day (https://news.ycombinator.com/item?id=3817840) shows a mix of bewilderment and belief that this is a defensive play. Very few people actually opined that Instagram represented much actual value.
Yeah, I admit completely that I thought they were massively overpaying for Instagram at the time. I also shared the highest OP's sentiment that I didn't think FB was a good investment for the same reason (that people would migrate from FB to the next thing as fast as folks moved off of MySpace).
I was absolutely and utterly wrong on both accounts. Part of it was definitely wishful thinking, though, as I dislike FB by one or two orders of magnitude more than any other software company.
But yes, I'd say their acquisitions were not completely obvious slam dunks.
They also tried to be Snap, ofc, but my recollection is that Snap refused. Interestingly, folks have probably flip-flopped over the last few years in wondering whether that would've been good or bad for FB.
And it was a no-brainer that it was something that should never have been allowed to happen due to antitrust regulations. T-mobile had to jump through hoops to buy decrepit Sprint but tech companies get to buy whoever and whatever they want that allows them to expand even outside their niche and where their niche is going.
I would posit that you don't use that data to decide whether or not you should buy Instagram. You use that data to decide if you should clone Stories, build an events platform, etc. IOW, it's incredibly valuable to be able to see aggregate user behavior, which is why Amazon's ownership of so much of the commerce experience makes their introduction of competitive "Basics" so interesting/anti-competitive.
I don't have any inside info here, but they could have gotten much more granular information than how many people were using Instagram and WhatsApp.
For instance, daily time spent in using Instagram on a per-user basis, whether that use was associated with a drop in Facebook use, and how patterns in that relationship broke down across demographics.
I didn't think they were no-brainer acquisitions at the time, but they've certainly turned out to be in hindsight. Was Facebook just smart or lucky, or did they have a lot more data than we did to judge those decisions?