OpenID

It's an interesting concept. It seem to have many strong supporters like AOL, Yahoo, MS, and Firefox. I think we would be better to know the concept of OpenID.

(http://en.wikipedia.org/wiki/OpenID)
OpenID is a decentralized system to verify one's online identity. While it is not intended to prevent spam or create a trust metric,[1] it solves the single sign-on problem without relying on any centralized website to confirm digital identity. OpenID users identify themselves with a URI or XRI which they own, such as for a blog or a home page. Since OpenID is decentralized, any website can employ OpenID software as a way for users to sign in.


And CardSpace is an alternative solution from Microsoft to the OpenID.

(http://en.wikipedia.org/wiki/CardSpace)
Windows CardSpace, formerly known by its codename InfoCard, is a framework developed by Microsoft which securely stores digital identities of a person, and provides a unified interface for choosing the identity for a particular transaction, such as logging in to a website. Windows CardSpace is a central part of Microsoft's effort to create an Identity Metasystem, or a unified, secure and interoperable identity layer for the Internet.