Sign up for the daily CJR newsletter. By the time the US attacked Iran, on February 28, half a billion dollars had been wagered on Polymarket, one of the world’s top prediction markets, predicting when the strikes would happen. As when the US invaded Venezuela, reports began to spread of new accounts making six-digit profits, which attracted speculation about people with prior knowledge of the attack betting on it. Ethical concerns grew when a user made five hundred thousand dollars by correctly predicting the date of Ayatollah Ali Khamenei’s death. Not long after the war started, Polymarket added a note to its Middle East markets. “The promise of prediction markets is to harness the wisdom of the crowd to create accurate, unbiased forecasts for the most important events to society,” the company wrote.…