How many AdWords advertisers is targeting your websites?
And how many do you block?
In our "Ad Review Center", we have about 50 advertisers and we block about 10% of them.
Since we dont give AdSense much of our impressions and we only use AdSense for image ads (to fill unused banners inventory) I can imagine that some of your sites must have hundreds if not thousands of advertisers targeting your sites.
Fabian