SFC explicitly does not do that. I eliminated the transparent registration mechanism, and very likely will not be adding it back in. Essentially, it’s confusing to the user because they’re creating an account on the site and passing personal information without knowing it.
This is silly. The whole reason to add a Facebook login to a website is so the user does NOT have to go through a registration process. But SFC requires that you first register BEFORE you can connect via your Facebook account. Who the heck is going to jump through that many hoops just to be able to login via Facebook?
I tried signing in with Facebook and got the same error everyone was getting. There was absolutely NOTHING intuitive about what had gone wrong. It was only after doing a google search that I found this thread and figured out the problem. No user, or very few, will bother trying to figure it out. They see a Facebook Login, they click it thinking they can sign in to your website without going through a registration process. If that doesn’t work, they’ll simply move on. I doubt 1 in a million would be upset that this process registered them with your website especially since the Facebook prompts clearly state you are passing your email address to the website. In fact, I bet most people actually think they ARE registering with your website when they sign in through Facebook.
Just my two cents. The Facebook Connect plugin provides this functionality and I’ve already deactivated SFC. It also provides a Facebook login button as a sidebar widget which bizarrely SFC doesn’t do.