Decentralized online identification system OpenID can log you into thousands of social networking sites (and counting) using a single username and password. OpenID asserts who you are by proving you own a URL—not an email address, not a password, not your mother’s maiden name, just a URL that must be confirmed by both the accepting site and OpenID host. No more filling out web site registration forms! Now that sounds wonderful to those of us sick of tracking the login details for all the web services we use. However, while OpenID is terrific in theory, it’s real-world usage still has a way to go. Let’s take a look at some of the pros and cons of OpenID.
http://lifehacker.com/software/technophilia/one-openid-to-rule-them-allor-not-302156.php
It’s definitely opens my eyes. Go check it out yourself.