I’m not sure exactly how they do it, but Goldman Sachs has an incredible ability to receive credit for being smarter than they probably are. Consider this from the Wall Street Journal’s Opinion page (gated):
In fact, the firm’s real talent isn’t knowing what the price will be, but what the price is. And Goldman clearly hit the mark with the $50 billion valuation implied by its $450 million investment in Facebook last week. The firm also rigged up a deal to make $1.5 billion in Facebook shares indirectly available to its well-heeled clients, and every sign is that the offer was oversubscribed.
If the offer was oversubscribed then Goldman clearly did not “hit the mark”. Having more willing buyers than shares to sell means the price was set too low and Goldman left money on the table – to the detriment of their clients, the existing shareholders of Facebook.