mhansen - 7:07 pm on Oct 1, 2012 (gmt 0)
I think Google is only telling a small part of the story by saying this update goes after emd's.
We have a 4+ year old, 8-page website that sits on an EMD for a phrase that generates about 25k monthly exact-match searches. It was untouched during this update for the most part. (Lost 1 position from 2nd to 3rd on the exact match query, personalization off, verbatim, etc)
I have however seen a few non-emd domains suffer with what looks like a -950 (end of results) penalty (more info [webmasterworld.com]) based on over optimization, or at least a high saturation of keyword phrases.
What it all leads me to believe is that:
1 - G* rolled out an EMD algo change. (affecting low quality emd's)
2 - Because of that EMD change, G* also recalculated the algo that relates to over-optimization (maybe related, or close to a Penguin signal?)
3 - The results we are seeing are only partially related to the EMD drops, but other changes can be related to any number of other factors and algo updates, NOT related to EMD, but a result of the complete data recalculation.