I’ve always enjoy reading plasticbag.org and one of the post was on OpenID. As quoted from his blog.

Quote
OpenID—fundamentally—is a solution to the problem of having a million user accounts all over the place. Instead of getting hundreds of user names all over the place you go to a site that provides OpenIDs and choose one username and password. These sites then give you a pretty simple web address which is probably easiest to think about as a profile page for you. Then when you want to sign into any other site on the Internet with an OpenID all you do is type in the address of this profile page. The site you’re on wanders over to that address, the other site asks you for your password, you tell it your password and then you’re bounced back to the original site where you are logged in and can get on with your business unfussed. Sometimes the local site will ask you if you want a different user name. That’s all there is to it.
Unquote

What strike me is that the Singapore government started one sign in function for all of their government portal long before this OpenID concept came about. Something simple yet no one really start to think about it in bigger scale until OpenID.

Check out plasticbag.org for more.