Many business with access to all the data Google has would take actions like this in the blink of an eye.
Sigh, so are we comparing horribly unethical to less horribly unethical?! These are the types of apologist's arguments that make me "sarcastic and cranky" on this board.
More importantly, this would blow a hole in their "why we aren't trying to monopolize the selling/buying links marketplace and everyone else selling links is evil and will be punished" argument.
Rest assured, the statute of limitations on this action is carefully being watched.
That requires some semantic indexing that can't be too far removed from the phrase-based indexing that Google uses for the organic results.
In fact, THIS argument is less probable than the less "Google-friendly" arguments. IF this argument was indeed the explanation, we would see massive changes in the SERPs that would be obvious to EVERYONE, not just the top 1% of adsense sites and adword buyers who are benefiting from what's actually happening.
What I wanted to ask is if a site runs Adsense does that seem to help in the SERP?...
I also wouldn't put it past the Big G to implement a +1, +2 scenario in the algo for using Adsense and Adwords.
Nor should you. And as I said before, this issue simply doesn't affect 99% of websites, so they would have no idea what was going on. (or benefit from it) And among the 1% it does affect, either a vast majority are unaware of it too, or have no reason to complain.