I know this sounds silly, but I just got a big win by split testing more ads on my site. I was always an advocate of not bugging the visitor too much, so always stuck with one ad.
Tried by best to optimize that one ad by testing size, position, etc. Finally found 2 good performers.
Then I just tried putting them both on the page. Check out the results:
So before I would get either $3 CPM or $7 CPM. Now with both combined I get $9 CPM, and since they're unobtrusive it doesn't bother the visitors too much.
Yay for increased earnings!
I'm now wondering about trying 3 ads, so just thought I'd ask the experts out there - how many ads per page is too annoying, in your opinion?