tedster - 5:57 pm on Sep 6, 2010 (gmt 0)
My first thought is "of course they know this". However, this is evidence that the organic SERPs are determined by how well Google feels they serve the end user. There are a lot of posts here that accuse Google of promoting sites that use Adsense - you've just pointed to the opposite.
IMO the presences or absence of Adsense on a page does not have any direct affect on ranking, positive or negative.