Radley Balko defends the Obama Administration's decision to stop defending DOMA in federal court and suggests the same approach should be taken in other cases:
As a client, the federal government is quite different from an accused murderer or a patient in a medical malpractice case, because it is supposed to represent the interests of all Americans. And while it's true that one of the president's main responsibilities is to enforce the country's laws, he also has a duty to uphold and defend the Constitution, which is not the same as latching onto whatever interpretation of the Constitution favors the government.
...the Office of the Solicitor General has never really been seen as a place for a president to express his policy preferences. But perhaps it's time to start seeing it that way, and to start holding presidents accountable for the positions they instruct the office to defend.