PPC_Chris - 2:00 pm on Jun 9, 2011 (gmt 0)
Here is an update on this issue if anyone is interested:
April 11: Hit by Panda 2.0, organic traffic drops off tremendously
April 25: Decided to remove 97% (97K) of indexed pages via 301 redirects (about half of pages de-indexed by May 23 at a rate of 1-2K/day)
May 23: We switch the pages from 301 redirects to 410 (de-indexing of pages continues at 1-2K/day for about a week)
June 1: De-indexing of pages slows to a few hundred pages/day with some days seeing no change
June 9: A huge drop of indexed pages, down to about 8K
I'm not exactly sure what to make of this, but this has been my experience trying to get pages that Google could see as low quality out of the index.