I'd enjoy a 3rd party login manager that is a separate system from Facebook. Some place where I can view all sites that I have authorized, manage my communication settings, and keep track of who I've registered with. I don't want facebook to know this about me.

I'd be more comfortable with Google doing this. It would simplify my sign in process for new websites, reduce the number of accounts and passwords I need to manage, remove the need for a password manager like 1password, and give me quick access to disable or block access to sites I no longer want to have an account with.

A startup could tackle this, but they would have to build trust and widespread adoption.