Del.icio.us seems like a great way of connecting with people with similar interests although when I tracked a few tags I didn't find any useful connections - the hit rate may be quite low unless you are after something very specific. I think it would be better as a research tool rather than a social interaction tool. Tagging could be more specific if it wasn't a single word tag although obviously words can be joined by a dash or underscore. I set up an account and tagged some sites but need to go back and spend more time on it.
I love that you can access your bookmarks from any computer - great appeal!