i dont doubt that the demand for facebook will be huge, but there's a few difference when comparing to LNKD ipo.
1. LinkedIn wasn't a big player in the secondary market pre-ipo. Facebook already has many shareholders, of which a good amount probably want to unload.
2. LinkedIn was the first social media IPO, therefore there was quite a bit of hype.
3. Because LinkedIN was the first social media IPO, no one really knew how to value it. The underwriters probably had a lot less numbers to deal with in determining what price to set it at, therefore there was a bigger room for guesstimating
4. There's a much better understanding as to what Facebook is really worth, so the underwriters will probably have a much better idea of the IPO price range than they did with LinkedIN.
5. Facebook paid $2 Billion for instagram, a company valued at $500 million only a week before the purchase.