Everything I read here (good stuff incidentally) says Google is screaming "Adwords" at anyone hoping to get traffic from Google.
No-one appears to have mentioned it here but it's widely believed eBay have suffered some kind of penalty with regards to results placement. the eBay.co.uk site is down to 40% of the traffic it had this time last year. Obviously proof of Google doing something to manually tamper with results placement would be in stark contrast to their own mission statement. On the other hand, I assume everyone notices that large sites seem to be getting dropped into supplemental, unless they are owned by the big guns eBay, Amazon etc. Interesting Google recommend ODP. Can't remember the last time the Google directory updated.