ichthyous - 1:21 am on Oct 8, 2012 (gmt 0)
Ok... the most obvious change that I can see is that since the weekend there are a lot more sites that at least look halfway legitimate suffering from -950 that used to rank. The number of sites sent to the end of results has at least doubled - if not tripled in the past week.
Some sort of penalty is definitely being applied to legit sites. My site just got pushed down to top of third page for an important term that I was ranking top of 1st page for years. Suddenly my site has been banished overnight...very strange. First noticed the change on October 1st and no improvement since. Overall WMT reports a drop in impressions of 32% and drop in clickthough of 35% in the last week, so lots of terms were affected. I thought it was due to changes I made on my site over the weekend (i.e. shortening page titles, adding canonical url tags, etc. but now I see it's a Google algo change