Hmmm.
That tells me one of two things. Either Goldman Saschs have their heads firmly buried where the sun don't shine with that valuation, or they're right about it and in that case, the implied value of the company pretty much has to come from the commercialisation (read advertising) opportunities it offers, and a good deal of that pretty much has to come from data mining information members provide. And that tells me that there's no way this side of hell I'll ever give them any of my personal information.
If I ever join Facebook (which is extremely unlikely), it'll be with fictitious information, starting with name and DOB, and if I do that, is there any point in joining at all?
The more I see of operations like Facebook, the less I like what I see.
Farmville and all that crap is a bit of a cash cow, as well. But yeah, it's a bit of a pie in the sky guesstimate.