" . . . a currently popular view of proposition bets, the "prediction markets" view, often treats prop bets or idea futures as purely information-distribution mechanisms, with the only incentives supposed as the benign incentive to profit by adding useful information to the market. This fails to take into account the incentives such markets create to act differently outside the market. A "prediction market" is always also one that changes incentives outside that market: a prediction market automatically creates parallel incentives to bring about the predicted event. For example a prediction market on a certain person's death is also an assassination market. Which is why a pre-Gulf-War-II DARPA-sponsored experimental "prediction market" included a prop bet on Saddam Hussein's death, but excluded such trading on any other, more politically correct world leaders. A sufficiently large market predicting an individual's death is also, necessarily, an assassination market, and similarly other "prediction" markets are also act markets, changing incentives to act outside that market to bring about the predicted events. http://unenumerated.blogspot.com/2015/05/small-game-fallacies.html