Bank of America this week announced that it is sharply curtailing its mortgage business with Fannie Mae, partly because of differences over buyback demands. The company said it has stopped selling Fannie purchase-money mortgages and refinance loans that are not originated under the Home Affordable Refinance Program. The problem, BofA said, resulted from a mutual decision by the bank and the government-sponsored enterprise not to renew a delivery contract that allowed the bank to sell loans to Fannie efficiently. “While we continue to have a valid agreement with Fannie Mae permitting the delivery of...