I am of the opinion that civilization is an extremely thin veneer and we forget this at our peril. Nature, be it at the chemical, microbial, plant, or animal level (this includes us) is all about equilibriums. There is no static decisive point for a species other than extinction.
Surferbeetle

I think this is a great point, it takes very little to disrupt the current politcal/social balance, but that doesn't mean an insurgency can't be defeated. If the insurgency is the disrupter, it must be defeated to return to an acceptable equalibrium. We may be talking past one another with vague concepts, such as "defeat" when talking about insurgencies. You defeat an insurgency using several lines of effort, and one of those LOEs is removing their cause(s) to continue fighting, thus making deals with the insurgents can be a LOE in order to establish or re-establish an equalibrium point. The idea that we never negotiate with the enemy is usually seriously flawed, but we do want to negotiate from a superior position. There are no book answers, it always depends on the nature of the insurgency.

Where we frequently get it wrong is:

1. The USG attempts to define success criteria, which leads to the USG taking the lead role in a counterinsurgency, instead of a supporting role. Who ultimately defeats the insurgents, the USG or the HN?

2. We attempt to transpose Western values upon non-Western societies, which in itself results in non-equalibrium.

3. We frequently fail to understand the nature of the conflict we're embarking upon before embark. Iraq for example, in my opinion, should not be viewed as the COIN model we base our doctrine on. As I have argued before, we need to develop a doctrine for occupation/regime change for situations like Iraq and Afghanistan, and possible future scenarios.

When I first wrote about it I called it regime/occupation doctrine, but my boss more accurately called it revolutionary war. Think about it:

a. We invaded a country and overthrew their government.
b. We just didn't replace the leader, we imposed a foreign form of government upon them in the midst of the fight.
c. We provided the bulk of the fighting forces, and still provide a significant portion of the fighting forces, thus we are in fact foreign revolutionaries, we are engaged in revolutionary warfare.
d. Counterinsurgency doctrine is wholly inadequate for this type of warfare. Equalibrium is a long ways off, since we significantly disrupted the social-politicalsphere. Something close to the former equalibrium may return if we see a military coup in Iraq and the re-establishment of martial government.

In a more traditional COIN scenario where we are in a supporting role, I agree that equalibrium may be the U.S. exit point, then the HN carries on with the transformation needed to decisively defeat/end the insurgency. In Iraq what does equalibrium look like?

We must take into account that our interests don't necessarily dovetail with the nation's interests we are supporting. We need to clarify the interests of both nations before we embark (of course you couldn't do that with Iraq, because the follow on government didn't exist yet, another argument for revolutionary warfare doctrine), and attempt to define our exit point before we enter, so military planners inconjunction with other key interagency players can work towards an endstate. This is challenging enough, but not near as challenging as what we're doing in Iraq.