or a funeral director or a mutual fund manager: "If youre an invasive cardiologist and Joe Smith, the local internist, is sending you patients, and if you tell them they dont need the procedure, pretty soon Joe Smith doesnt send patients anymore." Armed with information, experts can exert a gigantic, if unspoken, leverage: fear. Fear that your children will find you dead on the bath- room floor of a heart attack if you do not have angioplasty surgery. Fear that a cheap casket will expose your grandmother to a terrible underground fate. Fear that a $25,000 car will crumple like a toy in an accident, whereas a $50,000 car will wrap your loved ones in a cocoon of impregnable steel. The fear created by commercial experts may not quite rival the fear created by terrorists like the Ku Klux Klan, but the principle is the same. Consider a transaction that wouldnt seem, on the surface, to create much fear: selling your house. Whats so scary about that? Aside from the fact that selling a house is typically the largest financial transaction in your life, and that you probably have scant experience in real estate, and that you may have an enormous emotional attachment to your house, there are at least two pressing fears: that you will sell the house for far less than it is worth and that you will not be able to sell it at all. In the first case, you fear setting the price too low; in the second, you fear setting it too high. It is the job of your real-estate agent, of course, to find the golden mean. She is the one with all the informa- tion: the inventory of similar houses, the recent sales trends, the tremors of the mortgage market, perhaps even a lead on an interested buyer. You feel fortunate to have such a knowledgeable expert as an ally in this most confounding enterprise.   Too bad she sees things differently. A real-estate agent may see you not so much as an ally but as a mark. Think back to the study cited at the beginning of this book, which measured the difference between the sale prices of homes that belonged to real-estate agents themselves