I just realized my forum has been around since before 2003. It's been completely turned off for over a year though, all it was getting is spammers and it kept getting hacked. Working on converting it to a new system with a better registration system to try to counter the spammers.
Forums don't make much money though, it's mostly all repeat users, and most people use adblock now. The only way to make money through advertising now days is to have your own ad system that uses non standard image sizes and does not use any kind of ad server but is locally hosted, so that it just looks like an image that's part of the site, then programs like adblock should not block them. The people who use annoying crap like flash ads and popups ruined it for everybody else.
I actually got a google cheque for 100 bucks the other day, probably the first time in a year that I get one. There's always the odd person that may have forgotten to install adblock after reformatting or something.