October 2, 2008 | Washington PostPrediction markets have been around in one form or another for decades. Throughout the 2008 presidential campaign, Intrade has generated nearly $50 million worth of futures contracts. Betfair, a market based in the United Kingdom also attracts millions of dollars in bets. Its Web site predicts nearly $70 million will be invested on the U.S. presidential election. U.S. law prevents predictive trading nationwide, with the exception of the IOWA ELECTRONIC MARKETS, which began as an academic research tool and today caps investments at $500.