@Tedster, what form might the proof take? And what other possible explanations do you feel make the most sense?
At least one major (big data set) study that shows strong correlation between increased Adsense earnings or at least bid prices) and even one of the factors that people suggest are made to drive up Adsense income. Several companies I know that have access to big data sets have tried and not found it. If they ever succeed, it would be huge news, not something held quietly in the back rooms.
I do think we should consider theories that end with "...and then Google makes more money"
Absolutely - you've got to ask the question. The only problem with that is that Google almost always makes more money.