The thread seems to have narrowed its focus from insurgency in general to Afghanistan. I believe that Afghanistan is a bad case to study if you are seeking to construct (or argue about) a taxonomy for insurgency, because it is as close to unique as any war can be.

1. By 2002, Afghanistan was ungoverned. The occupying power (that is us) then proceeded to try and impose a central government on the population. So far, not much different than what occupying powers have done for time immemorial. But we attempted much more than just creating a national authority; we sought to construct an entire governmental structure reaching down to the district level, disenfranchising both the traditional (tribal) and organic (warlords) local power centers. Moreover, this had to be a government that could survive the withdrawal of our forces at some unspecified future date, so it had to gain a certain amount of popular support - in other words, it required 'legitimacy' beyond that afforded through the right of conquest.

2. Unfortunately, we allowed competitors to arise who were trying to fill the governance vacuum at the same time we were. The difference between 'us' and 'them' is that they have no intention of withdrawing, ever. They will be able to sustain their version of an Afghan government with their bayonets, rather than rely strictly on popular support or legitimacy.

3. Even at this late date, there are still spaces in Afghanistan that have neither insurgents nor governance. In essence, we are acting as both insurgents and counterinsurgents. In some areas, we are trying to establish cadres, recruit supporters, and extend political power into virgin territories; in others we are locked in a contest with competitors seeking to do the same; in still other areas, we are conducting classic counterinsurgency or guarding sanctuaries for a weak central government whose goals increasingly diverge from our own.

I can't think of too many historical examples paralelling what is happening to day in Afghanistan. Therefore, using it as a case study to validate or invalidate the RAND study is a bit unfair. In taxonomical terms, Afghanistan is the platypus of the insurgency world.