Christopher Caldwell tackles the topic in the latest TIME, explaining why the lines about personal responsibility don?t really pan out:

For those too poor to buy insurance, there will be a sliding scale of federal subsidies. That is where the problems start. If subsidies are too generous, you get socialist medicine by stealth. If the subsidies are too stingy, you get a huge new burden placed on the middle and working classes. Is it fair to call a requirement that we all buy insurance a tax? Conservatives say it is, although they would. A larger question is whether it is constitutional for the Federal Government to order citizens to engage in private business transactions. It’s hard to say. Few governments have had the effrontery to try it.

A human life is a different kind of commodity than a car. Supply equals one. Demand equals infinity. A person who flat-out refuses to insure his car can be deprived of the right to drive it. What do you do with someone who flat-out refuses to insure his body? For reasons that owe more to the Hippocratic oath and the Golden Rule than to the U.S. Constitution, you must treat him anyway. So what does it mean to promise, as the President does, that illegal immigrants won’t participate in our new health-care system? It seems to mean they won’t participate in paying for it.