Decius - 9:45 pm on Oct 25, 2010 (gmt 0)
My domain was on the first page of google for a certain keyword.
I added a sitemap to my site, on the site (a number of links to internal links).
Main page was removed from all searches for that keyword. Other internal sites still ranked, main page still showed up when doing the site:www.domain.com search.
Concluded it was because keyword saturation became too great because of the sitemap (links are text too) so I removed the sitemap.
Site was off front page for about 2 months.
On October 20th, removed sitemap.
On October 25th, site is on first page, similar rank.
So it took approximately 5 days for the filter to be removed once it was fixed.
Thought this would be helpful since I couldnt find such data elsewhere.