In April 1996, Oprah Winfrey hosted a talk show about the possible emergence of mad cow disease in the United States.The infectious agent of mad cow disease (which is thought to be caused by feeding cattle the ground-up carcasses of infected sheep or cows) eats a hole in the brain of both cows and people who eat the infected beef. At least twenty deaths in England were attributed to the human equivalent of mad cow disease, Creuzfeldt-Jakob disease, in 1996. After a food safety activist advised how the disease is spread, Winfrey exclaimed, “It has just stopped me cold from eating another burger!” When Winfrey’s show aired, cattle prices dropped dramatically and continued to fall for two weeks.

After Winfrey’s show, Paul Engler, a Texas cattle rancher who contends he lost $6.7 million in the...