Remember "death panels" and "socialized medicine?" Fear-mongers didn't derail health reform. Now, conservative opponents are pinning their hopes on the courts.

They're taking aim at the so-called individual mandate. That's a provision in health reform bills that requires all Americans to have insurance. Those who don't would pay a financial penalty.

It isn't only conservatives who dislike the mandate. Some liberals complain that without a strong public option to keep premiums in check, the mandate would benefit insurance companies at the expense of middle-class families.

But while the left grumbles, the right is mobilizing. A small but vocal contingent of conservatives argues that the mandate is unconstitutional and promises a court challenge.

Meanwhile, legislators in Missouri and several other states have introduced bills that would exempt their residents from the mandate.

All the constitutional arguments — about the mandate or about the ability of states to "opt out" of federal legislation — are great fodder for people who like to argue.

But the requirement to get health insurance coverage is designed to solve a very serious issue that experts call the "free rider" problem.

Insurance is a way to pool risk. Most people won't be diagnosed with cancer or another serious illness this year. But those who are face devastating financial consequences.

The sickest 5 percent of Americans account for almost half of all health care spending — an average of more than $14,600 each in 2006.

The sickest 1 percent account for more than 21 percent of health care spending, about $41,600 each.

Health insurance minimizes the risk of financial catastrophe and provides security. But to keep it (relatively) affordable requires the broadest possible risk pool containing both the healthy and the sick.

That system breaks down if some people — so-called "free riders" — are allowed to wait until they get sick to buy coverage.

By opting out until they face big medical bills, free riders shirk their financial responsibility and impose higher costs on the rest of us.

Insurance companies limit their risk from free riders by excluding coverage for so-called pre-existing conditions or by charging very high rates to people with chronic illnesses.

But under health care reform, that no longer would be an option. The alternative is an individual mandate. It has worked well under the Massachusetts health care reforms.

Opponents say a mandate infringes on the rights of people who may not want coverage. But in reality, it's those free riders who infringe on the rights of the rest of us.

Free riders want to go it alone as long as they're healthy. But when they get sick — and sooner or later, everyone does — they turn up at hospitals where the rest of us help pay for their care.

In the past, hospitals received payments from Medicaid to care for the uninsured. Under health care reform, much of that money would be redirected. So free riders who can't pay threaten to bankrupt hospitals upon which the rest of us depend.

An alternative to the individual mandate exists: We could allow free riders to opt out of the insurance system altogether.

But it would have to be a permanent opt out. No buying coverage later, when they eventually grow old or sick. At that point, to protect doctors and hospitals, the previously free riders would have to pay cash — in advance.

Who'd want a deal like that? Certainly not conservative politicians leading the charge against an individual mandate.

They've already got good health insurance, paid for by the rest of us.

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