1script - 2:48 am on Aug 25, 2011 (gmt 0)
In my case I can see a small but noticeable 15-20% drop in the amount of search queries shown in WMT for each of the banned sites approx. two weeks before the ban. The date does not jive with the official Panda schedule though - the drop happened on Aug 4th, the ban - Aug 21st.
Has anyone with a Panda devalued site noticed previously indexed pages being completely de-indexed?