what do we know about &filter=0

focusing on this issue

[dibbern2]

I am creating this thread as a supplement to the long one about the serp problems so many of us are presently experiencing. I've found strange results using the &filter=0 option, and wonder what others here are thinking it reveals, if anything.

For what its worth, this is my specific situation:
1. 20 pages from a 50 page site went from top 3 ranking to vitually unlisted (500th place or worse). This happened twice- I run 3 sites on different subjects, but built along the same lines. 2 of these sites have been hit in the same way. One site remains untouched.

2. The missing pages are all affiliate sales topics. (Seems like an obvious issue, or is it a red herring? I have other affiliate pages which still rank well.)

3. Using the &filter=0 option, my pages rank 1st. I find this odd, for its almost never 2 or 3, or something else.

4. Using the option, the 2nd through X serps listings are all the rest of my site pages that link to the missing pages. After x (about 15th place) the usual competitors appear.

5. I don't think my pages have been duplicated elsewhere on the web. The usual scraper sites have linked to me, but that's almost universal these days.

Are there other issues which you've discovered that might help us figure out the nature of this filter?