CollaborativeRank is an attempt at building a search engine for del.icio.us that returns helpful/timely search results. The central idea behind CollaborativeRank is to motivate people to provide helpful/timely URLs by rewarding them for doing so. Currently, the rewards are as follows:

• greater influence on search rankings for a given query
• a higher ranking as an expert for a given query
• a higher ranking overall among all contributors

I believe that these rewards would give people the feeling that they are having some influence over the URLs that others visit. I suspect that many people would feel a sense of satisfaction from influencing others in this way.