Last night the Inside AdWords blog announced two main things. The first is that Google will be "improving the algorithm for evaluating landing page quality and incorporating landing page content retrieved by the AdWords system." The second is that some (I believe many) AdSense publishers will see the impact of the landing page quality score.
We'll begin incorporating landing page quality into the Quality Score for your contextually-targeted ads, using the same evaluation process as we do for ads showing on Google.com and the search network. Advertisers who may be providing a poor experience on their site will notice that their traffic across the content network decreases as a result of this change.
I expect Jen to come back with a longer piece on the impact this has on AdSense publishers. I just wanted to get a quick post out there asap.