We have added a Facebook login that is currently activated for Standard Universe.

The main reason behind this is to provide an easy option.
FB login is an add-on to current system. Users in Standard will be able to login the universe both through the classic way and Facebook.

There is nothing more to it right now, Facebook it is not necessary AT ALL (if you do not have a Facebook account, no need to bother).

Facebook Login is in Beta and in the future it might be added across all universes.