How about charging users $1 per year for the mobile app. If this were to happen it would either make people stop using mobile (unlikely) and they will resort to

How about charging users $1 per year for the mobile app. If this were to happen it would either make people stop using mobile (unlikely) and they will resort to using the website (which is good for FB) or make a billion per year in revenue. Plus this would change the dynamics of free apps forever. I think it would be interesting for the mobile app ecosystem as a whole... more people would charge for apps.