Or when you buy a new car, suddenly *everyone* seems to have that car.
Back on the casino theme...hate it in blackjack when people blame someone for hitting and "messing up the cards."
Back to the subject at hand...I don't monitor many terms, but I haven't observed a shift in rankings toward Adsense-friendly sites, either. Some sites have added AdSense, which caused an increase in AdSense in the top sites. But, like you said, saying that the Google SE loves pages that have AdSense would be mixing cause and effect.