I've written a longer response to this post. To save your comments box and summarise:

• OPENID is a far more weak, time-dependent, and trivial assertion than is generally understood.
• Dreamwidth asserts that Livejournals have OPENID in place without checking; this is negligence.
• When publicising OPENID, Bradley Fitzpatrick explicitly said that it's not a trust system. Dreamwidth's use is beyond the design.