"People have been trying to use URLs as identifiers for people (as OpenID does), as it has great readability/discoverability properties, but this effort has largely failed because of UI/UX design failings, user confusion about URLs, etc.
It's now increasingly accepted that email addresses would be good identifiers for people (since that's what people are used to already, and have on business cards and in their addressbooks, etc.), but we're back to the original problem that email addresses are write-only. If I give you my email address today, you can't do anything with it except email me. I can't attach public metadata to my email address to give you more information.
WebFinger is about making email addresses more valuable, by letting people attach public metadata to them."
