May interesting insights provided by the Wired article.
"Does this site have excessive ads?" While that was a question asked early, there's nothing to indicate that this wasn't incorporated into the algorithm modification they eventually rolled out. Tom Critchlow posted a lengthy comment [seomoz.org] at SEOmoz where he suggests that there's a possible correlation between the ratio of unique content to advertising above the fold and how much sites were impacted.
It goes without saying that there's a certain irony in this if its true, as the advertising carried by so many of the impacted sites is served by Google. While I'd hesitate to say that "the search team and AdSense team are at odds with each other" I can certainly verify - having worked on large content sites - that their is a very deliberately maintained wall between the two.
That they used quality raters in validating this update is no surprise, as this is a standard procedure. (I once encountered a Google quality rater at a party. Despite alternately plying him with beer and peppering him questions, I'm afraid I have nothing useful to share with you all.:)