The greatest threat to Apple's ( AAPL) dominance in the portable music player business won't come from other consumer electronics manufacturers, Edgar Bronfman Jr. said Monday.Instead, it will come from operators of wireless telephone networks. Bronfman, chairman and CEO of Warner Music Group, suggested it wouldn't be long before operators such as Vodafone ( VOD) become major distributors of music via third-generation networks and cell phones with memory comparable to that of current portable music players. Those network operators, said Bronfman, have advantages such as a secure, piracy-resistant network and distribution base of phone-carrying customers much larger than the 5.7 million iPod portable music players that Apple has sold. "Ultimately," said Bronfman, "that's the biggest competition." Bronfman's Monday presentation at the UBS Media Week Conference in New York shed light on the strategic thinking of a key player in the music business. Bronfman, formerly vice chairman of Vivendi Universal ( V), earlier this year led a private investment group's buyout of Time Warner's ( TWX) WMG, and is reportedly planning a public offering of stock in the coming months. But while Bronfman made a compelling argument Monday that digital technologies harken a promising future for the music business, he has had poor luck in the past in converting a strategic vision into a profitable investment. Bronfman was a big backer of onetime Vivendi chief Jean-Marie Messier's attempt to create a worldwide media conglomerate from a French utilities company. But Bronfman's investment in Vivendi, along with that of other shareholders, tanked as Messier's strategy collapsed and Vivendi suffered a cash flow crisis. In his discussion of the state of the music industry, Bronfman indicated that he believed a weak fourth quarter -- finishing out a year that started with strong year-over-year growth -- would lead to full-year 2004 sales that will be flat with 2003 or slightly up.