Asking that people should "appear to want to job very badly" (and on a later comment changed to suggest they should be "dying for the job") is not merely about not phoning it it, or not being likeable.
About the "dying for the job" comment, though, I agree that is going too far. Personally, I think you should project a positive attitude about both your previous job, and about the possibility of working at the new place. But never act in a way that implies you aren't on equal footing with the interviewer. It should be a discussion, not a petition.