Did you test with adsense by placing just 1 ad unit in your page? Did you earn more??

I agree with the posters above of finding the right balance. Just test some different positions and units and check your earnings, and always keep your visitors in mind. For me the right balance is one wide skyscraper and one horizontal link unit.

 

i just made some change on my site too. before i got 2 ads blocks (with low revenue) and now i increased to 4. let see how it's go and i will tell you all the result later XD.