I am a forum owner, and I've seen some rough months with adsense. Please share your experience with adsense on your forum.
My forum have good traffic but the CTR is about 1% only. Compare to website / blog, the CTR is abit lower. However, the traffic is much better
When people click the ads the amounts are pretty good. It's getting them to click on the ads is the problem
adsense dont work well on forums. try making a good niche website content if you want to earn more. if your site is focused on forums, just add cpm based ads in order to earn more..
My forums have less than 1% CTR also. However, use forums as a tool to send traffic to your blogs and websites. ie. As admin, use the announcements and stickies to promote your links.
Try changing the layout of the forum now and then. Sometimes a skyscraper, sometimes a horizontal banner. Keep testing what ad size and format works best.
Not much success with Adsense on Forums so I have moved to Bidvertiser and Adbrite to see which one works well for me.