I'm not saying it's accurate. Frankly, it could be way off, but nonetheless it's entertaining to plug in sites that you frequent and play around with the numbers or compare. Even if it isn't very accurate.
However, regarding pennyarcade making less than expected, it could possibly be a result of the above site tracking advertisements that come from google or other ppc networks only and not having access to ads that come directly from an advertiser (like the Konami one here). The later are far more valuable. The bigger the site you are the more you're going to leverage your power for direct advertisement access.