I have installed yesterday Ultimate Facebook plugin and asked a friend to test it.
I noticed that, when user clicks on ”Login with facebook”, and auto-registers (one-click registration activated), his/her profile is created as a ”Subscriber” for the main blog, ”nextblog.ro” in my case.
This is sligtly different by the default registration procees, where the new user, registers an account, but does not gets a Subscriber account for the main blog also.
I wonder if this might be a security issue in the future (e.g. allowing unauthorized users to modify pages and posts on the main blog) or I shouldn't bother at all.