I can see the potential for this tool. This would be useful to have 'your' bookmarks available to you at work, at home, or anywhere. Although, if you are looking for a particular web site, I am sure you could just 'Google' it and find it just as easy. I liked being able to tag my sites, but this is the same as keeping them in categorized folders.
I also created an account, added favorites to it, and added the del.icio.us icons to my tool bar which made it much easier to tag and add the web sites to my favorites.