On a recent Saturday, at a bar in New York City’s Tribeca, a couple of hundred young sports fans in T-shirts and baseball caps ordered light beers served in tall glasses and shouted over a bellowing sound system under the confining fluorescence of 57 televisions. It was raining hard outside, but the weather didn’t lessen the excitement of the crowd, which was watching the second round of the N.C.A.A. Division 1 men’s basketball tournament, or March Madness.

As likely representatives of the 68 million Americans estimated to have bet on the tournament last year, a percentage of those who studied the flatscreens that day had inevitably lost money gambling on the games. The group of men in their mid-20s who I stood with at a counter were an illustrative party—before arriving for the 7:10 P.M. start of North Carolina State versus Oakland, our quartet had already squandered hundreds of dollars on various bets from the weekend’s preceding contests.