For a long time Google has been fighting the Made for Adsense (MFA) war against the quick money seekers who can often make the rest of us look bad because they prevent our entry in the search results.
In August of 2006, Google started its crusade against these sites by implementing a quality score for landing pages. That knocked some out of the AdSense game, but many survived.
It looks like they’ve made progress since then and are finally winning the war for good search results. Maybe you’ll never land on a junky, useless site again. To read the detail about Google taking action against these MFA sites, hop on over and read AdSense Disabling Arbitrage Sites.