incrediBILL - 3:52 am on Apr 17, 2011 (gmt 0)
I don't think it's color, big red herring (pun intended) nor are ads above the fold an issue, or as big as issue as people might think.
From the list of sites being discussed on this thread they all have something blaring in common to me from first glance: syndication and scraping.
They are either sites providing content for syndication or using syndicated content, meaning in either case the content is duplicated all over the place, including scraped versions. There is something about certain syndication mash-up sites, or even their original authors, that is obviously triggering a penalty yet not so for others.
I would dig deeper, I think there has to be a commonality about the type of content being penalized and what types of sites it shows up on. Some sites hit by Panda still rank well for one page and nowhere for the next page that used to rank well, and it's those that pages holding all the clues.
The human factors involved could've simply been:
"Same old crap. <click> More of the same crap. <click> Crappity crap crap. <click>"
Probably more to it than that, but mostly I'm seeing redundancy of non-unique content as a mobilizing factor.