I was playing around with creating a blog reputation snippet when I noticed the OpenID addition to blogspot. Interestingly, different blogs by the same person seem to have different OpenID Urls. This is a deviation from the regular conception of one identity per person. Even blogspot allows registered users to comment on blogs by indicating the people, not specific blogs by them. Not only does this approach confuse the idea of user attributes, it also increases problems multiple identities for a single person (the problem that OpenID wants to solve ?) This comes in a time when Google OpenID proxy exists (Google API at the backend I guess).
There was also a column that listed trusted sites, the ones a user 'remembers' always. On a side note, there were blogs that claim that OpenID are prone to phishing by rogue service providers (relying parties). I had written about different approaches to defeat phishers, including two factor authentication on the identity provider and identity images (like the one on Yahoo mail).
However, a simpler approach would be just to display to the user, all the relying parties he has logged into, everytime a user invokes OpenID. In addition to being useful, this some information that only an identity provider knows. Faking it would be hard as the attacker would be required to know the profile of the user, something that becomes increasingly difficult to guess as the usage increases. Most identity providers already show the user this information, it may as well be used as a part the anti-phishing part.
Just an idea.... :)