The booming mortgage market of recent years has attracted untold numbers of people hoping to get a piece of the action. And opportunities were bountiful all the way from primary market originations to investing in the burgeoning array of new MBS products. Now, as originations slow and profit-margins are squeezed, a new breed of MBS investors are butting heads with lenders, according to Stephen Ornstein, a partner at Thacher, Proffitt & Wood. “The secondary market…