You don't understand Facebook's revenue at all, which is why you think that. App developers spend hundreds of millions per year promoting games. They aren't making the big money from businesses that lose a couple grand and then find out it's unprofitable. They're making their money from Zynga.

That's sustainable. Facebook is probably going to make their own payment platform mandatory for apps, and they rake 30%. They could quite easily grow to a couple billion in revenue if nobody new ever advertised there again.

Also, local advertising does much better there than most stuff. Better than on Google in some instances.