Several Internet eons ago, I registered for a newfangled xri:=john.panzer universal identifier after listening to a conference presentation. Didn't know if this system was going to go anywhere or not, but I did know that it was free to stake a claim in this potentially interesting namespace.
Well, after a while I did get a free i-name, a contact page, and now it turns out I can actually use it to log in to something useful, to wit, the new OpenID Wiki. Turns out that the library used for the Wiki authentication automatically supports user IDs like =john.panzer; it just works. Which is of course the goal of the technology, and a good demonstration that user centric identity can become ubiquitous.