jimbeetle - 7:49 pm on Oct 14, 2012 (gmt 0)

I believe this is an over-optimization penalty

Matt Cutts specifically said "low quality" sites. When Penguin was released he mentioned over-optimization (being the engineer that he is he quickly changed that to "spam"), so I don't really see him saying one thing when meaning another.

Has anyone with significant non-matching traffic also seen that traffic fall off when this new EMD algorithm kicked in?

With the concurrent Penguin update and everything else going on folks are in a thorough state of confusion. (Heck, I'm sure there are a few folks in this thread who don't really know what EMD means.) And I guess it's possible that a site could be hit by both EMD and a Penguin refresh that would only muddy the waters more.