I'd been meaning to find those quotes anyway; back in January, a few skeptical people wondered whether Google "has a disincentive to algorithmically weed out the kind of drivel that exists for no other reason than to make its publisher money via AdSense" -- that's a quote from http://news.ycombinator.com/item?id=2127937 .
What the last two earnings calls show is that Google is willing to accept an impact in our revenue to improve our search quality. So it was a helpful exercise for me to track down the relevant bits from the earnings transcripts.
After all, you are displaying ads that someone has paid for, so if someone isn't clicking on them, then maybe the content is no good for the ads (ie poor quality). Likewise you can tell by how much someone will bid on the keyword how valuable the content is.
I'm obviously pursuing you into a spot you can't go, and for that I apologize, but the relevant problem here was your quoting a commenter from a blog who claimed from the earnings discussion that the effects would be transitory. That's a little too much indirection and terseness for my tastes. I also lost track of pronoun antecedents. In particular, I read it as transitory in terms of partner performance, when I guess it was meant to be transitory in terms of Google earnings performance? Still a bit unclear there. It's not worth chasing down myself, and we've beat on it enough. I was more concerned about somewhat-famous-person-makes-blanket-pronouncement-which-goes-unquestioned stuff, which is trashy for the quality of the site. Appreciate the clarification and additional resources provided for anybody who cares about this more than I do.