Andem - 6:57 pm on May 9, 2012 (gmt 0)
Heh, funny that you mention the 404 errors gs1md. I still have around 5000 links from a domain that expired going on 2.5 years ago and where the links only existed for a couple of weeks after noticing I had configured apache incorrectly and was "catching all" and had some duplication issues.
On that note, I have around 101 "Soft 404" errors which just won't go away, even though I'm clearing returning either 301s or 410s. They come and go as they wish, as I can see on the error line graph.
To be frank, I have my doubts as to whether the teams at Google really are so disconnected from each other. I wonder if the rubbish results we've been seeing for the past couple of years in the SERPs have something to do with similar bugs in their search engine algorithm.