Ive never seen so many bearish articles about a company before. That's probably a good sign if you are bullish on FB... Here in Sweden we have brokers who market how to short FB big-time!
Apple went public in 1980 at ~100x earnings and is up over 15,000% since then.
I'm not saying that Facebook is Google or Apple, but there's a lot more to analyzing a company than looking at P/E and calling it a day.