Friedman Billings Ramsey recently revealed that it is closing its MBS underwriting unit, an operation that a spokesman described as a “non-core” part of FBR’s business. The move comes on the heels of a restructuring in which FBR split off its investment banking, institutional brokerage and research/asset management businesses into a new entity, FBR Capital Markets. The transaction was valued at $270 million and left FBR holding about 70 percent of the capital markets business...