I should have been clearer: I'm not advocating anarcho-capitalism, just having an academic discussion. My point was that a state isn't necessary to enforce contracts, although the competing entities that would theoretically replace the state are quite state-like in many ways as you point out. The Icelandic Commonwealth was anarcho-capitalistic though, wasn't it (anarchy + property rights)? Worked okay for a few hundred years.

I do see your point that anarcho-capitalism isn't really anarchism, though. The societies they envision are radically different.