I can see where you are from and I kinda agree with it. I think we should invest in FB carefully. But if you wanna use P/E for your decision, you should short Amazon. They have something like trailing P/E of 1000 (or infinity?).
Honestly, stop looking at these stocks on a rational financial basis. You could have used this analysis to short GOOG, AMZN, TSLA, NFLX, PCLN, etc. and you would be miillions in debt. How many stocks are trading higher than FB right now with non-existent P/E ratios due to negative earnings? "Investors" are chasing momentum and nothing else right now.
Disclosure: I have been in and out of FB, but currently have no position. I am hoping for a sharp pullback before the close today to take a long position. Low 40s could easily get tested next week (but, so could low 30s).
Without debating whether FB is currently overpriced or not I would first tell you to calculate the actual P/E using last years earnings, current year earnings/estimates, and next years estimates and not rely on what Yahoo Finance has on their site.