> But to see any user data you would actually have to be authorized as that specific user. I.E. a developer could test their app by logging in with their own FB account and using their own data but would have no capability to look at the raw DB entries of other users.

This is the status quo as of the 2014 platform policy changes.

The entire debacle is around the data retrieved (and saved) prior to that, which is what Cambridge Analytics has done.

> Or perhaps their could be a limited capability for developers to log in to their app as another user of it

FB Developer app has support for test users, who are marked as such.