The United States has seen a sea change in the way that publicly financed health insurance coverage is provided to low-income, elderly, and disabled enrollees. When programs such as Medicare and Medicaid were introduced in the 1960s, the government directly reimbursed medical providers for the care that they provided, through a classic "single payer system." Since the mid-1980s, however, there has been an evolution towards a model where the government subsidizes enrollees who choose among privately provided insurance options. In the United States, privatized delivery of public health insurance appears to be here to stay, with debates now focused on how much to expand its reach. Yet such privatized delivery raises a variety of thorny issues....