Spotify, the free Swedish streaming-music service that has generated 10 million European users in less than two years, has delayed its long-promised U.S. launch indefinitely. The company's founder, Daniel Ek, was uncharacteristically non-committal during a tech conference last month, and would-be record-industry partners remain skeptical of its moneymaking prospects: Just 750,000 European customers have upgraded to 10-euro-a-month "premium" subscriptions so far. "The service is quite good, it's fun to use and people enjoy it," says a source at a major record label. "What they have not done is articulate a business model that would seemingly work." The label source wouldn't entirely rule out a U.S. launch this year, but says it would have to be on a "test" basis, with a one or two year contract to see if the paid service catches on.