It looks like Google is changing the way they measure ad quality again. TechCrunch reports that Google will be factoring in ad position when measuring quality score, effectively removing whatever boost is provided by higher ad positions.
Google will also be making it easier for ads to appear above the search results – because a certain level of quality is required for an ad to appear on the top, the higher quality rankings from the first change result in more ads that meet the quality guidelines to appear above the search results. Result? More money for Google, of course, because more ads appear on top, which should result in more clicks.