Some Faces Don't Sync to FaceBook

When I sync tagged photos from iPhoto to FaceBook, some of the faces link to their FaceBook accounts and others don't (their names aren't hyperlinked to their accounts).

I've searched around the Apple Community for an answer, but so far nothing I've found has resolved the issue. I went through Contacts and eliminated duplicate entries and entered in the FaceBook usernames and e-mail addresses for the affected faces, but after tagging those people and sharing to FaceBook, they still weren't linked. I can't see any common difference between the Faces that link and those that don't either.

Any ideas? Thanks!