zoltan - 10:56 am on Mar 3, 2011 (gmt 0)

Indeed, on some of the sites, big AdSense ads (2 336x280 on top + a 160x600 on left) are occupying 80% of the screen. Without scrolling, you actually only see the ads...
However, this might not be the only factor, as my site that is affected is quite moderate on AdSense ads (for example on our homepage, we only have one 728x90 on the very bottom).