One thing that would hurt Facebook a lot is the perception that you can't make good money on apps, since they make a lot of theirs on mobile app advertising now

One thing that would hurt Facebook a lot is the perception that you can't make good money on apps, since they make a lot of theirs on mobile app advertising now. Not really clear how that would happen though - at the very least IAP games are making a lot of money, and carrying TV advertising budgets. Their business model looks pretty stable, assuming studios can deal with or defeat the fact mobile games tend to be short lived. They could lose a lot of small advertisers, the startups that throw some of their seed funding into Google and Facebook's advertising pools a long way before having a real business model if those companies dry up - but I don't see it coming close to killing them.