Perhaps it's my daily contact with the Library of Congress headings, or the fact that I use the same computer all the time, but I did not feel an instant affinity with tagging. I can see the use of having a web-based storage area for bookmarked sites, but searching sites based on what other people may have tagged them as seems a bit random. I think it would be quicker to Google in the end. I guess it's all what you're used to.
I bookmarked 2 personal interest sites: The official UK site for my favourite show "Top Gear", and the homepage for the Canadian Warplane Heritage Museum. The tags I chose were:
Top Gear: cars motoring topgear Clarkson Hammond May BBC
Canadian Warplane Heritage Museum: Canadianmilitary aircraft Lancasterbomber