On the internet, you just have to publish stuff (even private stuff) with discretion. Noone (not even mighty Facebook) can stop someone/'friend' from doing a cut-and-paste of your stuff to a public place. Email has existed many years without any privacy policy, and its largely based on trust and human discretion.

The point is that it's Facebook's walled garden. Their policies are visibility, privacy, and opt-outability and they have every right to boot out an app that can't follow the rules.