Ever tried to sell a diamond?
"De Beers' advertising slogan, 'A Diamond Is Forever,' embodied an essential concept of the diamond invention. It suggested that the value of a diamond never diminishes and that therefore a diamond never need be sold or exchanged. This precept, of course, is self-fulfilling: As long as no one attempts to sell his diamonds, they retain their value (assuming the cartel controls the supply of new diamonds). When, however, an individual is forced to defy this principle by attempting to sell diamonds, the results can prove illuminating. Consider, for example, the case of Rifkin's Russian diamonds.
In the fall of 1978, a thirty-two-year-old Californian computer wizard named Stanley Mark Rifkin discovered an ingenious way to become a multimillionaire overnight. While working as a consultant for the Security Pacific National bank in Los Angeles, he had learned the secret computer code that the bank used to transfer funds to other banks telegraphically at the end of each business day. With this information and his mastery of the bank's computer, he realized that he could transfer tens of millions of dollars to any bank account in America. The problem would be withdraw the money from the system. In early October, he devised a plan for siphoning this money out of the bank and converting it into Russian diamonds."
Edward Jay Epstein's The Diamond Invention - Have you ever tried to sell a diamond?.
Technology also threatens the diamond industry... check out Wired's How to make a diamond.