aristotle - 1:15 pm on Apr 26, 2012 (gmt 0)
I know everyone in prison always claims their innocent, but I have no clue why I would have been caught up in that filter.
In my opinion visitor behavior is a big factor in Panda. This includes things like visitors bookmarking a page as a favorite, or exploring other pages on the same site, or returning to the site later for a repeat visit. Google can use its Chrome browser to collect this type of information.
The publicity around your site probably caused a temporary increase in traffic in the days preceding April 19. This increase in traffic would have allowed the Chrome browser to collect a lot more data on user behavior, and this could have led to a Panda demotion.
But keep in mind that this is just my theory.