Its a great share. I have noticed the same thing for my blog sometime back then I have read somewhere one article of putting less ad units on your site increases CPC . At that time my site was having 3 ad units and three link units. And average clicks I was getting of 12c. Then I decreased two ad units and made it only one. And I observed for some days that my CPC is increased after that I was getting CPC of around 43c.
Its really useful guide. And I am waiting for the results of decreasing the ad units on your site.