> Think about it, they already know who you are because you are logged in with your account. wait. is that how it really works? does the FB SDK these other app

> Think about it, they already know who you are because you are logged in with your account. wait. is that how it really works? does the FB SDK these other apps use really require that? I mean: what if I don't have a FB account? what if I don't have the FB app installed?