Can Social Bookmarking Improve Web Search? [a paper]

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.

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:

http://www-users.cs.umn.edu/~echi/papers/2008-hypertext/2008...

THe PARC group's blog:

http://asc-parc.blogspot.com/