And oh, your post pushed a hot button of mine: comments by people who think they're being incredibly insightful by saying "the world is not fair" in different ways. On HN, I think we can assume that people are adults and understand such things. Sorry about the flame.
For an analogy, consider a murder trial. Someone stands up and says, "The accused stands to profit from the victim's death." Isn't that suggestion more likely to come from the prosecution than from the defense?
Mmmm... no, unfortunately Google is supposed to make money, and they make money mainly from adsense. I'm not prepared to accept that random algo modifications having big impact on their revenue are done without concerns.
And when you are at the same time the same company driving people to web sites (search) and getting profits from ads showed in web pages (adsense) something bad can happen as it is not a free market setup.
The effect on adsense revenue isn't even measured let alone used. The people who make decisions about changes to ranking algorithms don't even see the data on adsense revenue because we don't even have a system to collect it for ranking changes.
I work in search quality, and there are many metrics I have to collect to launch changes. None of them involve ads.