[hueving]

We are achieving the same security guarantee as before, just without the user pain. All two factor provides in this case is proof that you have the phone associated with your account. Why does it matter if the app does the legwork for you?

[grey-area]

We are achieving the same security guarantee as before, just without the user pain.

I'd argue that a corporation other than the phone company being able to read all your text messages is significant pain.

Given that FB seems to want to take over all communication between users (contact list/blog/email/photos/messaging) FB being able to track and access anything you do is the inevitable endpoint of such aspirations, but many people are not comfortable with that, and the farther FB go down that road, the more people they'll alienate.