As astounding as this number is - and the longer I think about it the more mind blowing it gets - Facebook is all-but the single-point-of-failure for an Internet that was designed not to do that.
I look forward to the day we build these new protocols (sharing, social graphs, even search) in open distributed ways - the day Facebook becomes AOL in other words. I'm just not sure how.
And if I was any non-US culture-aligned country, I would be wondering how to build that replacement - this is like television in the 1950s, but everyone around the world is watching NBC.
But boy does 100bn dollars look cheap now.