This is why it would be an extremely bad thing if either the Supreme Court or a Romney Administration and Republican Congress overturn the health insurance mandate in the Affordable Care Act but leave the stuff everybody likes. As Ezra notes here, we know exactly what would happen in that scenario because -- believe it or not -- we've already seen it happen at the state level.
Washington State passed an insurance mandate-cum-guaranteed-coverage-and-no-price-hikes bill, which is essentially what the ACA is, in 1993. The mandate was repealed in '94 but the rest left intact. The result: premiums spiked, consumers dropped their coverage since they could just buy the same coverage once they got sick, and 6 years later it was impossible to buy individual insurance plans at all in the state of Washington, because it was no longer profitable.
These are our choices if we're going to persevere in this asinine decision to have private middlemen greasing and fleecing our health care system. Either everyone has to pay in, and I mean everyone, or the middlemen have to be allowed to weasel their way out of paying for your health care and just let you die like they could in the days before the ACA. There aren't really any other options, that is, short of doing the obviously correct and sensible thing and putting everyone on Medicare, and even then everyone will have to pay in.
As it is, overturning the mandate is going to mean causing premiums to spike as healthy people game the system, dropping coverage until they get sick. Overturning the whole thing means a return to the days when insurance companies were gaming the system, the days of "pre-existing conditions" and insurance companies giving people the run-around in order to keep from fulfilling their obligations.