Hmm does everyones site apear when you place a &filter=0 , be cause my site does not show up, but maybe thats because of not fully destrubted PR through the sites and the loss of 90% of pages indexed. Another thing I noticed on of the redirecting sites has a cache saying nov.3 that was the day my site lost it visitors, could it be that its the site that causes the main damage, Im just thinking loud here.
I think you hit the nail on the head. Same thing happened when a 302 redirect showed up to my site. Went from 2000 searches per month to 200 and a search for "my site name" disapeared except for filter=0. I got them to drop the listing but it's still in the SERPS and my site is no where to be found. Seems the real danger is when they zap your home page. It's like it zaped the PageRank out of my site. Google toolbar shows PR3 (I know thats not a lot in the first place) but my DMOZ entry shows PR1.