I like Chris Wolf's take on anarcho-capitalism. He wrote a hilarious piece about how the players in a recent high school shootings were simply acting out their own little independent right to levy punitive force in an anarcho-capitalist fashion.
I can't find it now, but this is a pretty succinct criticism of his: Anarcho-capitalism: Institutionalized Civil War
More from him here: Google Search
I would think that the high school shootings better demonstrate what happens when the state arrogates a monopoly of force which precludes the individual arrangement of effective protection. The criminals involved were encouraged in their criminality by state schools as were their parents absolved from responsibility.
The permanent and exclusive assertion of force by a group of individuals intent on imposing their will on others is the definition of "government". Real contracts for protection, freely entered, would be far preferable to mythical "social contracts".