LAS VEGAS -- During a year-long gambling binge at the Caesars Palace and Rio casinos in 2007, Terrance Watanabe managed to lose nearly $127 million.

The run is believed to be one of the biggest losing streaks by an individual in Las Vegas history. It devoured much of Mr. Watanabe's personal fortune, he says, which he built up over more than two decades running his family's party-favor import business in Omaha, Neb. It also benefitted the two casinos' parent company, Harrah's Entertainment Inc., which derived about 5.6% of...