There's an important difference between sharing information with facebook, and allowing facebook to share your information with 3rd party developers.
Pure auth has value to developers who want to verify a user without requiring a handshake of verifying an email address, having to manage against spam accounts, and so on. Yes it's possible to have multiple facebook accounts, but there's significantly more friction in facebook's system than in any home-rolled system you're going to come up with. While at the same time, significantly less friction from a "steps the user has to take to log into your app" point of view.
Nor should they! But I don't think that's an argument against this auth product, which only works if a user has an active facebook account (ie has trusted facebook with data) to begin with.
It's another developer option, one flavor among many, that developers can use to make it easier for users to log in. Given the reality that most people actually do use facebook, I think it's kind of interesting.
Didn't everyone trust Facebook to begin with. That's how the world works. You have to trust people to begin trusting them (or an organization) - else you're going to be paranoid of the world and become sick. Facebook has violated that trust multiple times.
We are in agreement re facebook violating user trust in a variety of ways. The Anonymous Authentication product is more about what goes to 3rd party developers though.
Pure auth has value to developers who want to verify a user without requiring a handshake of verifying an email address, having to manage against spam accounts, and so on. Yes it's possible to have multiple facebook accounts, but there's significantly more friction in facebook's system than in any home-rolled system you're going to come up with. While at the same time, significantly less friction from a "steps the user has to take to log into your app" point of view.