In a suit filed Sunday in federal court in San Francisco, StubHub claims the Warriors and Ticketmaster are violating federal and state antitrust laws by coercing season-ticket holders to resell their tickets only through Ticketmaster."It is a looming threat for all sports fans," the suit said, predicting similar restrictions on ticket resales for other teams, resulting in higher fees and fewer services.The lawsuit focused on the company's arrangement with the team to limit resales of tickets by fans who couldn't attend a game, or by brokers who had obtained the tickets, starting with an August 2012 agreement between the Warriors and Ticketmaster to share resale fees.In recent months, the suit said, the Warriors have started telling season-ticket buyers that they would lose their rights to future season tickets, and to playoff tickets, if they resold individual-game tickets through any exchange other than Ticketmaster.The suit also accused the Warriors of trying to mislead customers into believing Ticketmaster was the only reliable resale service that could provide a "guaranteed" ticket.A "fraud alert" the team issued last August, for example, said fans were being warned about "the...