If Google used anything about Adsense as a negative organic signal, then content farms would quickly move to (or even create) a different ad platform or adjust their Adsense layout. In other words, I think it would be a very temporary fix, and that's not the kind of thing Google usually does.
Somehow, Google needs to find a better heuristic to measure the quality of the content as perceived by people - and the enticing thing about moultano's posts is that he says some programmers feel they've found it.
One of the Google patents does mention the possibility of using ads as a positive metric - the idea being that a top brand would probably not advertise on a crappy site. I never had any reason to think that approach was ever put in place.