After reading this thread, I just did a search on www2 and www3 for one of my favorite keyword combination. There is a single change in the first 100 results: one notably spammy site went down from position 11 to position 16. This same site used to be # 1 and #2 a couple months ago. I find that interesting.
I have seen something similar for another site that uses doorway pages and loads of invisible text. That second site is not totally disappearing, but it is sloooow-ly sinking lower and lower in the SERPs. I am enjoying watching that. :)