The Economist has taken a look at supply and demand of kidneys and concluded that the world would be better off if there was a legal market for trading the organs. Excerpt:

Many people will find the very idea of individuals selling their organs repugnant. Yet an organ market, in body parts of deceased people, already exists. Companies make millions out of it. It seems perverse, then, to exclude individuals. What's more, having a kidney removed is as safe as common elective surgeries and even beauty treatments (it is no more dangerous than liposuction, for example), which sets it apart from other types of living-organ donation. America already lets people buy babies from surrogate mothers, and the risk of dying from renting out your womb is six times higher than from selling your kidney.

The article points out that Iran has already legalized the kidney trade.

Meanwhile in China, The Daily Telegraph reports:

China to prevent transplant trade

China has acknowledged for the first time the scale of "transplant tourism" — in which the organs of executed prisoners are sold to foreigners — and are to force doctors to pledge to stop the practice.