Where Should the Doctor Draw the Line?

Last night I joined a colleague in a conversation with medical students about medical futility, the relatively infrequent but damaging dispute between a patient or surrogate decision maker demanding treatment and a physician who believes it holds little or no therapeutic promise. 

This morning I read online a Wall Street Journal piece on the apparently growing practice among pediatricians of firing families that refuse vaccinations.

In the first case, the patient is demanding therapy against the physician’s best judgement. In the latter, the patient is refusing treatment against the physician’s best judgement.

Clearly, “the customer is always right” doesn’t apply to medical practice. But in a system that treasures patient autonomy, when is it appropriate for a physician either to deny an available treatment, or insist on one? When must a physician do so?