CollaborativeRank is a project by Amir Michail of the University of New South Wales. See his partial draft of a paper entitled CollaborativeRank — Motivating People to Give Helpful and Timely Ranking Suggestions. He has a new version for tagging, probably a better environment, based on del.icio.us tags:
Users on del.icio.us who give meaningful tags to helpful/timely URLs (as evidenced by others subsequently doing the same)
will be rewarded with higher CollaborativeRank, which means that their tagging will have greater influence on this search engine’s rankings.