A big problem I have with these absolutely ridiculous numbers is the assertion then that Zuck is a multi-billionaire. Unless he's figure out how to turn investors dreams into a Scrooge McDuck vault full of money of course.
If I understand it correctly, though, couldn't Zuck have just sold some of his shares to an investor and gotten some money? Yes, not several billion, but he's rolling in a couple hundred mill right now, I'm sure.
I remember reading how several investors bought into Twitter by buying $100 million from one of the founders...
By the same token, he could have already sold most of it. $70B is the valuation established by those who have already bought shares, after all. It's in their interest to convince the rest of us that they got a good deal. Heck, if $70B is such an insane valuation, you'd have to be insane not to sell out at that price.
The public perception seems to be that Mark has many billions just sitting in the bank. It reminds me of the Business Week cover of Kevin Rose, basically saying he had $60 million lying around: http://businessweek.com/magazine/content/06_33/b3997002.htm
