Forensic Economics of 'Credence Goods'
According to the article, a Swiss economist found that physicians tended to perform less unnecessary procedures on other doctors and relatives of lawyers. Why? Because those classes of patients either had less of an asymmetric information problem or the supplier had strong incentives to not cheat their customers.
The Economist article also mentioned a research paper -- titled, On Doctors, Mechanics and Computer Specialists - The Economics of Credence Goods -- that found that, if consumers were cognizant of the 'credence goods' problem and took actions to remedy the situation, the market would re-align the incentives enough to substantially reduce the problem. The ideal situation (the equilibrium price if the theory pans out) would be where the suppliers of credence goods would charge a flat fee ... raise the prices of simpler services and lower the price of more complicated services.
By the way, I wrote a blog piece on the forensic economics of sports betting a while back that was in a similar spirit to this post.