The Treasury Department this week finished winding down its holdings of Fannie Mae and Freddie Mac MBS, claiming a positive return of $25 billion for the U.S. taxpayers from a market stabilization initiative launched in the teeth of the 2008 financial market meltdown. Treasury’s holdings of MBS issued by the two government-sponsored enterprises peaked at $197.6 billion in December 2009. “These MBS purchases helped preserve access to mortgage credit during a period of unprecedented market stress,” the agency said. The Federal Reserve agency MBS investment program was far bigger, peaking at $1.12...