The recent suicide bombing on the Indian Embassy in Kabul and the attacks in Pakistan reminds us, that Afghani violence is not purely a function of American military input, ie, Violence != Function( American Soldiers, Talibans). The violence there is a combination of tribal vendettas, Taliban/Al Qaeda ideology, American/Western presence, and Indian/Pakistani/Iranian competitions. We need to keep this complexity in mind as we debate our strategic aims for Afghanistan.
One thing people may not know much is the presence of Indian and Pakistani contractors and NGOs in Afghanistan. India is spending quite a bit of money on Afghanistan, both in buying influence and assisting its merchants in making American military money. Pakistani vendors and ISI operatives are, of course, already on the ground in Afghanistan. So part of the violence there is this low intensity conflict between Indian and Pakistani factions. The Karzai administration is embroiled in this battle, as well.
Robert Kaplan has a nice opinion piece on China's efforts in Afghanistan as well.
Therefore, many anti-coalition militants may be fighting to kick the Yankees out, but the recipe is there for the fighting to continue, long after we leave.