I have wondered for years why Yahoo haven't attempted to use del.icio.us as a back-end for some sort of search engine. I don't think it requires any great leap of faith that searching for a combination of keywords that numerous people have already tagged the page with indicates it's relevant.<p>Hell, even improving the searching in del.icio.us would be helpful - basic ability to sort by number of people who have saved a page would be incredibly useful, for example.
This research seems to overlap with their near neighbors at PARC, esp this paper (which isn't cited by the Stanford group:<p><a href="http://www-users.cs.umn.edu/~echi/papers/2008-hypertext/2008-04-29-hypertext08-tagging-info-theory-fp-046-chi.pdf" rel="nofollow">http://www-users.cs.umn.edu/~echi/papers/2008-hypertext/2008...</a><p>THe PARC group's blog:<p><a href="http://asc-parc.blogspot.com/" rel="nofollow">http://asc-parc.blogspot.com/</a>