Until the cash (not stock) is in your account, you have nothing. Considering the finicky audience and the trouble monetizing it, FB could very well pull a Friendster.

He cashed out as part of the second rounds of investing. I've heard numbers ranging from 50 mil to 200 mil.

The second round of funding was from accel and jim breyer.

He cashed out ~ $1 million, according to Sarah Lacy's book which she interviewed him for.