Rana Mumtaz stashed this in Instagram!
Instagram's valuation was solely determined by Mark Zuckerberg: http://pandawhale.com/convo/1072/in-facebook-deal-for-instagram-board-was-all-but-out-of-picture-wsjcom
Interesting... So nothing would be in the way for Facebook to dominate the social media world.
Until the next big thing comes along.
Draw Something got 50 million downloads in 50 days.
Angry Birds in Space got 50 million downloads in 35 days.
The right app can explode very quickly.