I don't second guess Mark Zuckerberg, as that is a consistently losing bet. That being said, there is no reason the price should have been $2B. The frothy prices, mean that a $100M company was priced at $2B and that dumped a lot of money from Mom and Pop to VCs.
Yet in the long term I'm not so sure. Facebook's revenue is built on doing things that cannibalize the value of their platform-- annoying ads, creepy surveillance, even creeper "experiments" on their users, etc. That's making them decidedly uncool. Network effects are holding their popularity high for now, but while network effects are powerful they are not unstoppable. Things can "tilt" at any time.
I think that's why Facebook is acquiring things like Oculus. If they're to become the next Yahoo they want to make sure they've invested in some other properties. That of course is why there's still a Yahoo-- the core Yahoo brand is almost worthless.
The bet is that Oculus will be used in many areas (not just gaming) and will become multi-billion business in the future. It a big bet and it could go wrong. Keep in mind that $2B is 1% of FB stock price - placing 1% bet on new promising technology is not unreasonable.
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