If AD revenue misses, and subscriber growth globally is down Y/Y this will tank to $ 20.
They will do whatever it takes to shine, hide, and take the emphasis off the poor growth in mobile ads, and the drop in subscriber growth.
FB is no doubt a fun place to work, they are an advertising company, but the internet ad space is beginning to mature, as more competitors come online, and as the economy is soft there is less spending.
But selling ads and making things cool for teenagers and a few other new users, is not sufficient to maintain these astronomical market caps.
They may introduce new ideas, somehow do accounting tricks, and maybe even do a share buy back to avoid the share prices from tanking down more than $5, and it may work, but sooner or later the market cap will reach equilibrium.
In my opinion I think FB is worth about $ 5 a share.