Please don't forget that OpenID Delegation means that I should be able to use any host I own and control to delegate for my OpenID at another provider. That means that beyond just having any number of id providers, from corporate and community driven, to personal or family based, you further have the issue of having delegation allow for anyone's domain or sub-domain constitute an id. E.G. my-popular-blog.com maybe delegated to popularblogger.myopenid.com.
