We are AdSense premium partners and have seen our revenues nearly cut in half while our page views remained constant. I can safely say this is due to the fact that a lot of our visitors use ad block plugins. I can't blame them - some ad formats are annoying enough to justify ad blockers. Unfortunately Google does not offer a way for us to receive ads on the server level and integrate them into the page content, bypassing the ad blockers - like Google does it on his own properties.