Generally it appears the FBC registration process is intended to work pretty much the same as the regular registration process with the exception that all the user credentials are snatched from the linked FB account, which of course makes email confirmation unnecessary. The one thing that failed to work on my site was that the moderator approval email never arrived. I tested the site with a new fake user registering the regular way, and I got both the email confirmation and moderator approval emails. So the site's email system is working and regular registration is also.
One CB configuration setting I found to be not set (not sure why as I am sure I set it when I created the site) was the registration "from" email. It was blank. After setting that and repeating the process, I still did not receive the moderator approval email.
The account is created and awaiting moderator approval, but no email was sent to alert me to the fact. This will create problems as I can't continually check the site for new registrations.
Thanks for a great plug-in!
Bruce