Wouldn't that be easily solved if all the other services offered a "log in with Facebook" feature and routed messages to other people who also logged in with Facebook?
I assume there's a gaping flaw in this idea that I can't quite see at the moment ;-)
Part of the gaping flaw is that Facebook will very quickly disable your API account so you can't offer login with Facebook, if you're competing with them. :)
I assume there's a gaping flaw in this idea that I can't quite see at the moment ;-)