I think everyone should read this by Peter Galbraith:
http://www.nybooks.com/articles/18150
Great insight on why Iraq is so set up for a prolonged civil war (and not just an "Iraqis vs insurgents" civil war...more of a Sunni vs Shiite vs Kurds civil war).
"There is, in fact, no Iraqi insurgency. There is a Sunni Arab insurgency. And it cannot win. Neither the al-Qaeda terrorists nor the former Baathists can win. Even if the US withdrew tomorrow, neither insurgents nor terrorists would be knocking down the gates to Iraq's Presidential Palace in Baghdad.
"Basically, the military equation in Iraq comes down to demographics. Sunni Arabs are no more than 20 percent of Iraq's population. Even in Baghdad—once the seat of Sunni Arab power—Sunni Arabs are a minority. To succeed, the insurgency would have to win support from Iraq's other major communities—the Kurds at 20 percent and the Shiites at between 55 and 60 percent. This cannot happen.
"While the Kurds are mostly Sunni Muslims, they have a history of repression at the hands of Sunni Arabs. A few dozen Kurds have been involved in terrorist acts, but al-Qaeda and its allies have no support in the Kurdistan population, which is one reason Kurdistan has largely been spared the violence that has wracked Arab Iraq.
"The Shiites are completely immune to any appeal by insurgents. Sunni fundamentalists consider Shiites as apostates, and possibly a more dangerous enemy than even the Americans. (The Americans, they know, will leave. The apostates want to rule.) For the last two years, Sunni Arab insurgents have targeted Shiite mosques, clerics, religious celebrations, and pilgrims—with a toll in the thousands. The insurgent goal is to provoke sectarian war, and they seem to be succeeding. In spite of calls for restraint by Shiite leaders, there are growing numbers of retaliatory killings of Sunni Arabs by Shiites."