I've just switched over to QuickConnect to handle my game's login and user registration sequences, however during testing there's been a few instances where I have to delete a user and start over on my game database, then delete the Player.IO registration.
I've noticed that there does not seem to be a way to delete a single user and related information for that user - or short of deleting them, banning. That would be a really useful feature to have across all databases on Player.IO!