Scott Lemieux had a good piece earlier this week on the Affordable Care Act and the individual mandate:
And the same goes for the power that Congress has to regulate interstate commerce. Ultimately, the best check against unwise legislation is politics. As the Constitutional was being deliberated, James Madison didn't believe that the specific powers of the federal government should be limited in advance -- not because he didn't believe in limited government, but because he felt that the multiple veto points within the federal government provided a more than adequate check on federal power. The fact that upholding the ACA might permit Congress to do something foolish down the road is neither here nor there -- the same is true of any government power. Arguments that the ACA is unconstitutional have to stand or fall on their own merits -- and the merits of the anti-ACA argument are ultimately weak.
The unique aspects of the health insurance market justify the mandate and limit it's application to a specific context. But to say that government, because it can tax you if you don't buy health insurance, it might be allowed to do anything, forgets the large number of built-in choke points in our political system that prevent government from just making you do anything. Sure, you could argue that leaves us at the mercy of the political system rather than the Constitution, but one thing both left and right should have learned by now, with our litanies of constitutional abuses aimed at the other side, is that we're really always at the mercy of the political system.