I don't think Google does a very good job of policing their ads. Or they don't care.
Please refrain from going click-crazy. Google supposedly has sophisticated algorithms (as well as actual people) that keep track of such things. If a forum with ~1800 members gets as many ad clicks in one day, it's going to look fishy. That would be an unheard-of click through rate and very suspicious.
If you see an ad for something that interests you, click it. If not, then don't. Simple enough.