Jeffery,
It is early days yet for tagging and the semantic web.
Shocking admission. I had a delicious account for a year-ish before I started using it. Didn't feel comfortable putting all my bookmarks in public view. Plus I wasn't sure about which social bookmarking site I should use. I learned del.icio.us has the most users and has the most valuable information for my purposes. I imported my bookmarks as unshared bookmarks and will share and tag them - someday!
Emma I haven't seen too many students using del.icio.us here either. Wandering around the lab I see web browsers email and facebook. I appreciate your comments about your experiences with tagging and social bookmarking - thanks for sharing them.