Tony Karon, in TIME, here
"...Other key factors in tamping down violence may yet be the cause of further violence and instability; these include the truce declared by the radical Shi'ite cleric Moqtada al-Sadr, and the anti-Qaeda alliance the U.S. forged with the Sunni insurgents of the Awakening Movement. Deep distrust remains between the Awakening Movement, many of whose members were aligned with the Saddam regime, and the Shi'ite dominated Maliki government..... But it may not be the situation on the ground in Iraq that determines the future of the U.S. military mission there. For one thing, the fragile calm in Iraq coincides with an increasingly perilous Taliban resurgence in Afghanistan,......Then, there's the financial crisis and looming global recession that will inevitably impose a far greater austerity on Washington. America's military deployments in Iraq and Afghanistan are expected to cost close to $200 billion for 2008 alone, and maintaining that commitment will become considerably more burdensome as Washington is forced to funnel many hundreds of billions of dollars into simply averting financial collapse...."