maximillianos - 6:35 pm on May 25, 2010 (gmt 0)
We do the switch between ads and no ads for folks logged in versus non-logged in traffic. We found that regular visitors (logged in) didn't really care to click ads much, since they saw them all the time. But new traffic (non-logged in) would perform very well with ads.
Works on our site pretty well with this setup.