I believe that this, like many tech stock, is way over inflated. It is way higher a multiple than it's profits would indicate as valuable and its growth has already levelled off. Some people had already declared it's IPO would be $100 billion, people are morons when it comes to valuation. Watch a few episodes of Dragons Den, listen to Kevin O'Leary - The numbers don't lie.
The only way to make money off the Facebook IPO if you aren't a current holder would be to play on the call and put options as there will be a great deal of movement on opening week. Ultimately I think it will launch at $5 billion, shoot up when the market open, maybe finish the day strong but ultimately putter out over the next weeks, months, and years as the excitement for the big social media IPO subsides.
At the very least while you could make a profit on smart plays, and maybe even a strong opening week rise it's not a long term stock - I've seen no offers of dividend and the market room for growth is minimal.
I'm not going to waste my money when I could make a better return on rich dividend stock such as electrical providers in brazil, while the market share price there is volatile the over all dividend return gives amazing ROI and the market still has room to stabilize and grow, that's a smart investment.
I've always wondered why people buy into something when it's already at its' prime, other than sentimental reasons it's a waste of money!