It's (according to the court) a Tax thing, not a Commerce thing. From the SCOTUS blog:
There were not five votes to uphold it on the ground that Congress could use its power to regulate commerce between the states to require everyone to buy health insurance.It was sold as "No, no it's not a tax...", I'm fairly sure I was telling everyone that it was always 'a tax thing.' Especially when they were hiring at the IRS to enforce the thing.
However, five Justices agreed that the penalty that someone must pay if he refuses to buy insurance is a kind of tax that Congress can impose using its taxing power.
Because the mandate survives, the Court did not need to decide what other parts of the statute were constitutional, except for a provision that required states to comply with new eligibility requirements for Medicaid or risk losing their funding.
On that question, the Court held that the provision is constitutional as long as states would only lose new funds if they didn't comply with the new requirements, rather than all of their funding.
It's also a liberty thing -- but we seem to have a lot less of that, and fewer people seem to care. Pass the broccoli before they force me to eat it.