I think ads plays a part in this panda update. I have a site that was hit the day panda was officially released and its a social network type site, and it has over 1.5 million members, the thing is all those member profile pages have ads on them (standard from the default template my mistake I know) so google pretty much sees the majority of the pages with no/little content on it and 3 banner ads. I had the ads removed from all user pages and submitted a reconsideration request.
If this is indeed a ad to content ratio type deal which I strongly believe does factor in (how much exactly we dont know) then google will be hurting themselves more than helping. People will start resorting to ways of hiding ads from googlebot and making sure only actual visitors see them then google will have no idea how many ads are on any given page. This of course will not work with adsense since they can effectively track the ad impressions on any given page