I've really been thinking about making forums for my literature site. I get around 30k uniques a month and I've got 1000 (and rapidly growing) people on my newsletter. So I think I could get them growing.
I just, I don't know if I want to take that plunge so to speak.
Its in a cost benefit stage right now I guess, and I don't know if I'd have the time to run it. I'd really like a partner for it I think, if someone wanted to run my forums they could keep all revenue generated by them.... maybe I Should go over to the trading post.
You can start by offering a free email discussion list for your members. See how many join up and how active they are. This would be a good gauge on whether it is time to build forums or take the plunge so to speak. By doing this you will have to dedicate a little time to moderate the list but it is a good way to feel the waters without a lot of risk.
You can start free discussion lists at yahoogroups.com and topica.com.
Another thing about starting a list is that you will be listed in their directories. This will bring you a small amount of dedicated traffic which in the long run will be worth more than any search engine placement.