You might want to read a bit on the reaction from the OpenID community. Your suggestion, as well as quite a few others, were brought up:
http://blogs.zdnet.com/digitalID/?p=85
Also, there is an on-going dialog on the OpenID wiki about possible solutions:
http://openid.net/wiki/index.php/OpenID_Phishing_Brainstorm
Posted by Scott Kveton at February 3, 2007 03:40 PM