Tagging

I can see real value in tagging worthwhile sites - I have a vast number of favourites bookmarked on my browser but it is quite unfriendly to use so the idea of a simple tagging system sounds great. Working in a library makes you want to see everything in categories so the standard browser favourites set-up just doesn't cut it.
I like the idea of having specific buttons/icons on your browser to go straight to del.icio.us rather than having to remember yet another login and password.

The cloud idea is great! - it is simple and easy to understand that "bigger is better", but having the ability to also view the list to see the number of items with each tag is also beneficial.