What advantages to social tagging do you see for libraries?

I played with CiteULike and it was really interesting.  One of my ongoing interests is looking at the idea of overload.  The problem is not getting to content it is sifting through it and getting good stuff.  A quick tag search found some other individuals and groups that are looking at information overload.  I was able to follow their citations and find some interesting review articles and such.  I also found that I could ask to be a connection to various people, making a research network.