I wonder if this option has been considered: if there is a link farm or span in search results, the content can be flagged as spam by searchers. If the flagged content was verified as spam by Bing, the people who reported it could get a point or some small reward. If they report sites that really are not spam, their credibility score takes a small hit, like in Jeopardy when you answer incorrectly. In this way the web could become a self-curated place. We've tossed around this idea at our <a href="http://www.insegment.com">Boston internet marketing</a> firm.