If you’re getting this it _probably_ means that the users account has been deactivated. It appears that the ‘remove app callback’ is not pinged when either Facebook or a user deactivate their account.

Unfortunately there doesn’t appear to be an obvious method for determining if a users account is active or not, the solution I use is to call: users_getStandardInfoand ask only for the first name. If you get an array back (in PHP you can useis_array) then the user has an active account, otherwise it’s inactive :)

Enjoy!