Some, though not all, of the health plans floating around Washington feature what is called an "individual mandate". The basic idea is to require every person to carry some form of health insurance. Without an individual mandate, some of the other "reforms" being proposed such as requiring insurers to cover preexisting conditions simply won't work. (If no one was required to carry insurance, and insurers had to cover preexisting conditions, why would any one have insurance coverage before they got sick?) Individual mandates were a big issue in the early stages of the Democratic presidential primaries last year. Strangely, Hillary was for them and the President was against them. Things have changed.
One question that isn't asked much, is this "Would an individual mandate be constitutional?" So far as I know, this idea is actually completely unprecedented. Never in the history of this country, has the government required, by law, that every citizen buy a particular type of product. Auto insurance comes closest, but I have two adult siblings who don't have auto insurance. One is a life-long pedestrian and the other lives in New York City and doesn't have a car.
The only possible place in the Constitution that would give Congress this authority is the Commerce Clause, which gives Congress the power to regulate interstate commerce. Now, the Supreme Court has stretched to Commerce Clause so much that growing wheat or marijuana for your own personal use constitutes engaging in interstate commerce and therefore subject to regulation by Congress. The Court, however, has also ruled that the Commerce Clause is not infinitely elastic, ruling that a federal law mandating gun-free zones around schools could not come under the Commerce Clause. So the question is, Does refusing to engage in an economic activity - that is, refusing to buy health insurance - constitute engaging in interstate commerce?. I would argue that, quite obviously, it doesn't, and that Congress does not have the authority to order me to do so.
It is also obvious that if this is found to be constitutional, it will not be the last "individual mandate" to come out of Washington.