Delicious is an interesting site. I have always kept my use of computers very simple. I don't bookmark, I don't use an address list on my personal computer. I don't want to take the chance of passing on a virus or other bad problems to friends I e-mail.
I like the idea of keeping sites I would like to bookmark on a website. It is neat that I can click on sites I listed and go to that site. That's really helpful. I have my students do some sort of research assignment for many of the units we study. I give them a list of websites to use to help them with their research. Sometimes students tell me about a site they have found and I try to remember to go back and add it to my handout I give them.
If I set up a Delicious account for each of my subjects, I can put on websites. Students can access them and add good ones they find.
I wish there were a way to create folders on Delicious, so I could group the sites around different periods of history. It seems that after a while, the list may get to long and unwieldy.
I think that would be a problem for librarians using Delicious. The list of websites could grow quite substantial and the only way to search through it would be by the use of tags. If you don't use the correct word, you could miss a great site.