The fall in Facebook shares since the IPO isn't much of a worry for the earlier investors. Peter Thiel sells 80% of his Facebook shares for $400 million. He bought his stake in the company for $1/2 million. Another way to look at it is that he made a 137% p.a. return in the eight years since investing.
P.S. 22 August
Actually, he made more than a 2000-fold gain.