lewis1 - 9:36 am on Sep 29, 2012 (gmt 0)
We have seven sites in a specific niche but they are all partial match domains. Four have been hit by this update. The other three, for now, appear to be ok.
All are UK hosted websites, running Wordpress. All on same server and all are running Adsense. They all share the same Adsense account.
Never wanted to hide anything from Google so kept everything together and we were open about saying all these sites are ours.
The only thing I can think that has triggered these four sites to get hit is the lack of link diversity. These are the sites have spent all year getting decent links for but the link text variation is low.
The three sites which so far seem ok have had less link work done to them and that is why perhaps they will be ok.
Therefore, my initial observation regarding what Matt says are "low quality" sites are those where the backlinks mostly contain the same text.
By the way, all of our sites have 100% unique well written content and are updated frequently. They are good sites and we have been very proud of them.
If on Monday this sticks our plan of action is to go and try and get all the link texts changed to give them some diversification. Not sure what else to try at the moment.
Will post update if I spot any other patterns.