How to require new WP registrations to use a Facebook ID/button?
Is there a tool or membership plug in that allows me to REQUIRE that new users register via a Facebook button (so I can grab their real email address, etc) ?
If they do NOT register with a facebook ID then I want to give only limited content access.
Also, is there a way in WP panel (or by some kind of site membership plug in) to block access to certain email addresses (to prevent them from registering)?