This plugin has multiple issues and does not perform well.
On a WordPress multisite setup:
1) If I try and register a new blog with a new FB account (email address not registered with site), and the FB profile has not location set, I cannot get past the registration page. I continually get an error on the Current Location field. Here is an image that describes this:
2) If I try and register with a FB account, even if the location is set (and the above problem isn't applicable), then I immediately get a Page Not Found error.
3) On the social theme, on the front page has an option to login in with username and password, but I am unable to figure out how to add the login with facebook button in that section.