To learn more about XAuth and why we're among the supporters of this technology, check out our post on the Social Web Blog.
From a technical perspective, we wanted to offer you some additional insights into how this technology works.
If you visit Meebo's XAuth page, you should see an array of logos:
When this page loaded, it requests the list of services that have been registered with XAuth by making an HTML5 window.postMessage request to xauth.org. As you can see in the graphic, no active sessions were detected.
Upon returning to meebo.com/xauth, the page requests the list of active sessions from XAuth, and passes the browser an array of domains that the browser will match against the local storage for xauth.org:
Once the tokens are retrieved the program iterates through them looking for matches, and then modifies the interface according the service token discovered, like this:
For more technical information about XAuth, please read the spec, or visit the informational page on xauth.org.