[redorb]

thats easily a million dollar question; figure out how Google could flick a switch and clean their index with out noticeable false positives - I think they would hand you a check :)

* i would assume that the problem parallels with spam emails. i think webpages offer more clues to what the page is about than emails though.

[jacquesm]

I would argue that it is orders of magnitudes more complex.

Spam passess a single toll gate on the way to each user. You have an address book with contacts and previous conversations and a whole pile of data about previous 'known good' emails in the inbox.

Spam filtering has gotten pretty good. A lot better than google at filtering out 'bad' search results.