This is from Wikipedia: Two major identity prdvoiers online, AOL and Yahoo!, can currently be used with OpenID. AOL's system, using openid.aol.com/username, is currently in beta. Yahoo has unofficial, third-party OpenID support at idproxy.net. Also, Flickr's login is now merged with Yahoo's, isn't it? As such, it would seem to me that using one method or another, an OpenID can function for Yahoo/Flickr or AOL/AIM, killing two birds with one stone, as they say.