[augustl]

A good example would be things like a todolist app and other personal things. It would be nice to make an app like that without having to also scale an entire set of servers and just have the syncing etc be provided by the user of the app instead of by me.

Something like that could even be integrated into iCloud if it becomes popular. Then your "user provided server" would probably only work with other Apple products, Apple style. But for many users that would probably be good enough.

And you wouldn't be limited to having only one of these "user provided server thingies", either.