SW SetGroup is used for example in the student council of ETEC KIT. There, each student has an e-mail address ending in either stud.uni-karlsruhe.de or student.kit.edu. All e-mail addresses that match this pattern will automatically be added to the student group and get special permission on the site.
If the Facebook log in plugin set the Facebook mail address as user mail address and you configure SW SetGroup with a regular expression which notice the Facebook mail address, yes.
We are launching a portal for specific customers and I was looking for a way I could allow them to register as many uses as they want but want to restrict registration specifically to clients.
It looks like, at first glance, this may do the trick.