Facebook, in my experience, is terrible platform for communities/groups as it's not designed for any sort of in depth, ongoing discourse.

Speaking of discourse, Jeff, I'm curious as to why you didn't mention WP Chat here? ( http://wpchat.com/ )

There's also a lot of active WordPress related groups on Google+ As a platform, G+ lends itself much more to community than Facebook does, in my opinion.

I nuked my Facebook account about 4 months ago and, for me, it was one of the best decisions I made in 2014. I may have to set one up again at some point for business purposes but I am putting that off for as long as possible!