Of all the things I have written about federation and identity over the years, I failed to make the critical link between reputation and identity. This is why I am only moderately enthusiastic about OpenID, it solves the smaller part of the problem.
Reputation and other trust models, like certification authorities, are critical to making federation work outside of carefully crafted agreements between partners. Until these trust models have been worked out, using an OpenID for anything higher-value than blog commenting will be risky. [From » Reputation taking center stage | Between the Lines | ZDNet.com]