I actually like the OpenID (since SO is one of the first sites I use that has it consistently implemented), but now I have about 5 accounts in varying degrees of answered questions. Is it possible to consolidate them into the primary OpenID that I am starting to use more and more as more sites are implementing it?
Email firstname.lastname@example.org and they can merge your accounts for you. Be prepared to demonstrate ownership of your accounts (probably posting a comment or editing your About Me section).
Send an email email@example.com explaining the situation.
If you can, edit the duplicate, and write in the description that it is a dup of your other account. You may also want to edit the description of the original. This will help prove that the person who owns the duplicate account, is in fact the same person who owns the other account.
I have actually done this, and it worked flawlessly.
I think that there should probably be a warning, if you are trying to log in with an OpenID that is not associated with any account.
( copied from my answer here )