Don't if this goes against what you are trying to do with it, but you should incorporate the forum with crossfacebook. The username and password for here could be the same for there. To me, if I was first approaching this site, I would be hesitate to sign up for two separate accounts to access two separate things. It might be more enticing to consolidate the two in that regard. That way you might be able to get more interest for each of them since it would encourage the use of both.