Medical privacy is ethically tricky. It (1) protects bad doctors, (2) makes it harder to develop treatments, (3) makes it hard for consumers to shop intelligently.
Medical privacy would be useful when negotiating cost of coverage with your insurer, but they have a contractual right to demand your complete medical record.
The best arguments I've heard for medical privacy are (1) you might not get a job if you're sick, (2) shame factor could prevent people from going for treatment and (3) you may not get a date if you have, say, herpes. (#3 is true but not necessarily a strong point from a social standpoint).