If claimID executes properly then it could insinuate itself into numerous aspects of our online activity. It will not become a nice-to-have or need-to-have but something that you just plain have. Everybody has an identity and everybody will have something on the internet proprietary to themselves. claimID is merely a manifestation of this concept that will be inextricably tied to us in the future.
Usability
Google grid (or Epic, or whatever its called now) could really gain from this since it can locate one person and show all the details that that person wants to show about him/her to the world. claimID's usefulness stems from how many people actually start using it, which is why I'm writing this so that whoever reads this will be fascinated enough to sign up for the beta. People can put their claimID addresses within their e-mail signatures, probably on their business cards. It has the potential to be something like your e-mail address, since its practically your identity in virtual space.
Its the one stop destination for anyone who wants to know anything about you. But claimID is not the governments way of keeping a tab on who you are! It works by feeding the information you want to the search engines, so that if someone googles your name, and you have a claimID, it'll show up with the relevant details as the search snippet. A simple idea, but very powerful ramifications in the long run.
The signup process is really simple and very fast, since its aided by AJ modules all over the place. You'll have to enter your e-mail address to get an invite for your beta, and once you get that, they'll take you to the signup page where you'll enter the basic details. After which, you can start linking pages, tagged under various names and put under categories as 'About me', 'Not about me' or your own category. You can see my claimID page.
Concerns
Throughout my signup process, I wasn't given any particular fields to fill up. There was my name, other names, location, and then there was a generalised 'template box' which asked me all the information I wanted to put. That scares me a little, since I don't want claimID to undergo the Myspace effect. I'm sure someone sometime will begin to use claimID the same way, but I hope they find a way to block such attempts.
This is really a very good step towards contextualizing data, and making them individuals related. I hope claimID gets bought by Google, because they will benefit from this if they are serious about having the Grid online by 2014. So go ahead! Claim yourself on the internet!