[Robert] Kuttner says the first red herring about single-payer health care is that it limits choice for the patient, and if you want proof look at Medicare.
Indeed, Medicare does very little to restrict patients' access to medical services. Let me explain that with an environmentalist analogy: overfishing. Saying, "We don't need to have any restraint on the use of medical services. Look at Medicare" is like saying, "We don't have to worry about the fish population. Look at all the fish we just caught."
Five hundred years ago, unrestrained fishing probably was ok. But over time, as the human population grew and our fishing technology improved, it became possible to wipe out entire species of fish. At some point, you need restraints--if not regulations, then property rights that create incentives for conservation.
Similarly, when Medicare was started in 1965, you could give people unrestricted access to the treatments then available. But over time, with the Medicare population growing and technology changing, the stress on the system is increasing. At some point, it will be unbearable. We are already approaching that point.