Every once in a while when I query: http://api.stackoverflow.com/1.0/questions/id I get a question back that is missing the owner field. Is this expected? I haven't seen anything about owner being an optional field for questions.
Sometimes there isn't an owner. The user has been deleted (usually), which is pretty rare in the grand scheme of things.
This is, however, an acknowledge deficiency in the API that will be resolved in a subsequent version (to return a
display_name, in all likelihood).