I work at Facebook. We use Facebook groups heavily for company announcements, discussions, funny posts, help and support, feedback and feedback requests, etc.

I work at Facebook. We use Facebook groups heavily for company announcements, discussions, funny posts, help and support, feedback and feedback requests, etc. We use Phabricator for code reviews and other software engineering tasks. Of course, not everyone uses Phabricator (because not everyone is an engineer or programmer), but I haven't seen anyone not use Facebook. Even the culinary team (for Facebook's cafes) has a few popular Facebook groups.