An Idea Doesn't Have a URL
I was attracted by an idea that emerged... "The idea doesn't have a URL." In other words, a tag can somewhat represent and idea. A URL can point to one slice or view of an idea. But it cannot be captured with either a tag or URL.
(Edited Oct 2006. There was a typo that made the last sentence not make sense. Changed the last word from "idea" to "URL." Thanks for catching that, Nick.)