Originally Posted by Blotch

I think a forum has become a success when it has become self-sustaining. By that I mean the community could take care of itself for a while without you. That means it makes enough revenue to pay for hosting and any additional costs the forum requires, there are enough active members to visit the forum and make that revenue for you, there are enough mods to moderate the forum, there are enough new registrations per day so that you don't really need to advertise anymore because word is getting around on its own, etc.