The search engine is heavily influenced by what they describe as the “Top 500″ del.icio.us taggers. This doesn’t just look at who bookmarks the most pages, but who bookmarks things quickly, and in ways that other people subsequently copy (affirming that you are tagging in a way that others think is appropriate).
In their own words, “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.” I’m proud to say that I made the list of 500 – #499 to be exact (oh great, another thing to compete over).
This is a great relevancy tool for searching del.icio.us content.
Collaborative Rank has a discussion forum here.