The #1 value added app for lots of people, whether they know it or not, is exportability insurance. Make an app that tracks everything externally so that if Facebook starts to suck, you can migrate the next platform.
The existence of that portability might actually ensure things never start sucking.
I think five years from now we won't be logging into Facebook but we'll be talking to our mobile devices and they'll be scheduling reservations for us (it will all be autonomous agents doing tasks/chores for us on behalf of our openID)
The existence of that portability might actually ensure things never start sucking.