(Reuters) - The world of fantasy sports is having to grow up fast.
Everything seemed to be going great for rapidly growing companies whose customers, after paying an entry fee, draft fantasy player lineups from a range of sports for periods as short as a day in the hope of winning big cash prizes. Investors poured money into the top two U.S. companies, DraftKings and FanDuel, ahead of the current National Football League season, the busiest time of the year for fantasy sports.
