steveb - 11:24 pm on Sep 9, 2003 (gmt 0)

I don't have anything good on this except an anecdotal observation, but I have one page that has been doing this for five weeks at least... Google does a middling update, it drops to 18th or 19th as "fresh" spam is introduced. Nothing happens for a couple days, next several days it climbs about one slot a day as spam is filtered out (or pagerank added, same effect) until reaching 12th or 13th, then Google has another "let's add some fresh crap" middling update and it drops to 18th. And then we go through the process again.

It's 13th today, except a jiggling tomorrow...