Google has been pushing hard lately to improve the quality of it's listings. Two major updates to it's ranking structure, Panda and Freshness, have recently kept SEO companies on their toes.
Google recently revealed a new update that will evaluate whether there is a balance between advertising and content, and it will make a quality judgement based on that balance. The search company will rule against websites that have too much advertising. Users find too many ads distracting and annoying, and now, that practice, can hurt your search ranking as well. One of our tenets at Ironpaper has always been that SEO and user experience should always align. If you attract people to your site by trickery, then you don't convert or users fly away in droves.