Did you ever know a librarian who did not want to cross reference things. Social bookmarking
tags info, ideas, opinions not just books. It offers one the the whole enchilada in a single package.
As with wikis this application is more like a group project. The benefit is that usually
other contributors may have an interest but a different perspective on your subject
which can broaden one's horizons. With one click so much information will be at hand,
then one can bookmark this info to one's own personal site. That info can be retreived
from anywhere, you don't need to be at the specific pc where it is on your favorites list.

I like the tagging idea for homework. We may be in different locations but the same county
so the same school system peobably the same homework. delicio.us has been adopted
by some saavy users, why not click into their sites for some good ideas.