You make an excellent point about using open-ended questions. In the course of performing a review of an operational loss at the bank,
I would first send out a questionnaire to the person responsible for posting the loss. The questionnaire I developed is intentionally designed to be open-ended with the hope that the person will provide more information than I even need.
My concern was that, if I made the questionnaire too specific, I would end up with very brief answers or would somehow end up leading the person into an answer. If I need more specific information after reading the questionnaire responses, I follow up with the person directly. The questionnaires also give me good background into the situation before I call them so that I can ask more intelligent questions (which also might be open-ended).