I'm concerned about a couple of issues;
- Facebook users seem to be very immediate stimulation seeking based on the endless short responses I've seen between my users. Especially because a good amount of content in the group comes from social media pictures and videos that of course is not as appealing in a forums design.
- I've checked tons and tons of forum communities (running Xenforo and other software) and they all seem to be very dead. Apart from the major big boards that already have massive communities, most regular sized forums get less than a handful of new threads everyday.
Maybe I'm basing my expectations on the activity of forums in my experience of using forum communities in the pre-social media days.