The U.S. mortgage marketplace is still strong, but it’s becoming increasingly competitive – and demanding – for those players that survive, according to some of the participants at the Bear Stearns Mortgage Finance and Housing Markets Conference in New York this week. Panelists noted that there has been some dramatic change in the marketplace recently. “It used to be the government-sponsored enterprises dominated the market,” said S. A. Ibrahim, chief executive officer for the Radian…