Right now if you share your account, you are doing so at your own risk. This cannot protect items from being lost, but can protect more importantly, your characters, or account in general. I would suggest using this question/password only when trying to delete a character, or remove an account.
This would NOT stop account sharing of course, but would help protect the owner's character/account. It wouldn't be needed to login, so there would be absolutely no reason to give it to another person.