Here are 2 scenarios, which would be better off? 1)A low CTR, but a lot of clicks from the same people. 2)A REALLY high CTR with a lot of individual clicks. I run a forum and my CTR has been .XX% and even .0X% The community is at about 200 people, with varying numbers being active everyday (20-50 average), with the size growing. With such a low CTR would the clicks cause problems if they clicked more? I've had to tell people to stop clicking after 3 ads, and have threatened them with bans for excessive clicking after some one joked about clicking 50(Luckily the person admitted that it was a joke). However, I feel that I may be limiting the people in their interest. Several of them have complained about not being able to click ads that interest them.
High CTR with lot of individual clicks are always cool. Anyway you can't expect more than 1% CTR from forums.