Megan McArdle links to this article by Graeme Wood arguing in favor of harvesting the organs of executed convicts. But wait! It turns out that most methods of execution ruin the organs. How do you get around that? Wood argues in favor of the "Mayan Protocal" -- executing people by removing their organs:
But by using what the bioethicist Arthur Caplan calls “the Mayan Protocol”—a term derived from the ancient Mayan practice of vivisecting their human sacrifices—the removal of organs would itself be the method of execution. If this sounds inhumane, compare it to current practices: botched hangings, painfully long gassings, and messy electrocutions. Removal of the heart, lungs, and kidneys (under anesthesia, of course) would kill every time, without an instant of pain.
I suppose you might find doctors willing to go along and ignore that "First Do No Harm" thing. And if you did, well, think of the lives you could save!
Given the overlap between libertarians and science ficiton fans, it's hardly surprising that "Lou," Megan's first commenter, brought up the Larry Niven short story, "The Jigsaw Man." To give away the punch line: in that futuristic society, they required that death row inmates have their organs harvested. As a result, legislatures expanded the death penalty to include more and more offenses, until the defendant in the story faces the death penalty for being a recidivist traffic offender.
I don't think that it would go that far -- but there are ample reasons why the citizenry ought not receive collateral benefits from criminal punishments. (Following this theory, David Friedman has trumpted the virtues of inefficient punishments.)