Fundamentally, the prospects for the shares are fairly bright. The company has blazing (though slowing) EPS and sales growth and no debt.
No one knows for sure what will happen after the shares start trading. In his book, How To Make Money In Stocks, William J. O'Neil the founder and chairman of Investor's Business Daily details a plan for trading hot IPOs.
He recommends letting the shares trade for six to eight weeks and to observe any price patterns formed by the shares. O'Neil uses patterns like "cup-with-handle, flat base and ascending base," to follow the accumulation or distribution of a stock.
In short, I would want to see how Facebook shares trade for their first month or so. If the shares formed a bullish technical pattern and then broke out, I might buy them. However, I would put a stop-loss of 5-8% under my buy price to reduce risk. O'Neil encourages the use of stop-losses on all trades. This method worked very well with Google.
It's possible the FB IPO will flop. The market is where this will be decided.