Sorry haven't commented on this earlier. I've been looking at trying to get a good way of automating posts from here to Facebook, currently I haven't really found a nice way of doing it without spamming everyone. There's a new version launching int he next few weeks which should make this possible.
You're right it's Facebook, our traffic significantly dropped once shortly after they launched their groups functionality. Compared to a forum it's pretty useless in regards to searching and usability etc. However it's there immediately in your hand where most people are checking all the time.