Fannie Mae and Freddie Mac must be encouraged to keep key employees so that the home finance system is ready for the biggest reforms in decades, their federal regulator said on Tuesday. Edward DeMarco, director of the Federal Housing Finance Agency, said “several key executive-level departures” at Fannie Mae and Freddie Mac over the past month is a concern as the companies work to improve internal risk management efforts and to break the foreclosure crisis. Greater uncertainty of employees is understandable since the two companies are unlikely to survive as Congress seeks out a new housing finance system, he said. But they should be comforted by the FHFA’s support, he said.