It started gaining currency during Justice Kagan's Senate hearings, if not before. And it has only grown in prominence since (mentioned in roughly 100 percent of legal briefs challenging the minimum essential coverage requirement). We have all now heard the question a hundred times, maybe many more:
If 1501(b) is constitutional, what prevents Congress from requiring every American to eat broccoli (or join a health club, or eat at certain government-approved restaurants, or purchase GM cars, or [fill in your own horrible and add it to the parade])?
Professors Koppelman (Northwestern) and Somin (George Mason) have an interesting exchange on the question (at Balkinization and the Volokh Conspiracy, respectively). Recommended reading.