Open Real Time Messaging System
Unless you REALLY trust the people who are managing your UIN/Username/etc on the server, you don't WAN'T them to share everything between themselves. Besides, in Europe, it's illegal for them to do so.
A far better notion is to have all that information available to YOU, and YOU decide what to share with them. However, this technology (like a digital wallet) has been around for a really long time in web-world and has been abandoned for now, mostly because people don't want to administer them. You move computers, you have to move the thing. Floppies suck, smart cards aren't everywhere.
Now once GSM with PID smart-cards come to the US and I can use one card for credit, ATM, computer security and phone.... yum.... pervasive technology with privacy rights...