My original thoughts about Walker proving to be the most likely:
From CNN updates:"• John Walker, the American who fought with the Taliban and was captured after a prison uprising near Mazar-e Sharif, has provided useful information to U.S. authorities, according to the chairman of the Joint Chiefs of Staff. Gen. Richard Myers told Fox News Sunday that Walker is not a prisoner of war, but a process was going on to determine his final status. (Full story) "