That's right. But while Amazon and Apple probably are not going to grow 5 times either, they have a proven business model and they are unlikely to lose more than 50% in value. The same cannot be said about Facebook that depends for revenue heavily on a few partners. Therefore the risk/reward ratio should be much better for Facebook (to get me interested).

I don't consider a factor of 5 or 6 extraordinary given the risk. Take a look at Intel or Amazon for their growth since they IPOed.

At a valuation of $75B to $100B, how much can we expect Facebook's share price to grow? Apple's valuation is now at $400B to $500B, so maybe 5 to 10 times at most while there is a considerable risk for not much growth at all. The share price of Amazon and Apple grew over 100 times since their IPO but this can't happen with Facebook because their IPO is coming fairly late. So, while the IPO is a great day for early investors, it's not worth it for average investors.