Because we love it ;-) and because you can have one OpenID login but use it for thousands of sites spread all over the web.
Get your OpenID at one of the lovely free (as in free beer) OpenID providers:
One Login, Many Sites
An OpenID is a single username and password that lets you login to any OpenID-enabled site. OpenID makes remembering different usernames and passwords for different sites a thing of the past (ice age like).
Getting One is Fast & Eeasy
In fact, you may already have one, without even knowing. Every AOL/AIM user has an OpenID address (example: openid.aol.com/screenname). Or you can quickly obtain one from an OpenID provider like myOpenID. It's free!
Works at Thousands of Sites
There are thousands of OpenID-enabled sites and more are getting on board every day. For example all of Amarok's web publications are going to migrate to OpenID step by step, also KDE is heading towards a unified OpenID access to it's web services.
It's an Open Standard
OpenID is a protocol made for the public, by the public. No one — not Google, not Microsoft, not Novell — owns or controls your login information: You do.
JOIN THE FUTURE NOW - GET AN OPENID