To make it more simple; what stops an organization becoming so powerful that it can use coercion to enslave the rest ?
Canarchy -> AnCap
Sanarchy -> Socialist Anarchy
Ah, thank you. So you are concerned that in an anarcho-capitalist society there would be nothing to prevent a powerful, malevolent hierarchical organization from assigning itself power and taking over. This is a valid concern. Let me ask you a question before I attempt to respond: What stops a government (even a democratic or constitutional republic) from becoming a dictatorial and draconian nightmere oppressing and enslaving its populace?
As usual it is difficult to get a straight answer.
The only thing that stops a subset of the population from enslaving the rest is luck. Luck has allowed the variance of the population's coercive distribution to become large. Therefore some individuals within the population have significantly more coercive power than the rest. Luck has allowed the set of individuals who have significantly more coercive power to form a distinct social group. Now this distinct social group has coercive power that is unrivaled by any other group. Again luck determines that the agenda of this social group involves enslaving the rest unopposed.
Short answer: The variance of the population's coercive distribution became to large. The laws of the universe will do the rest.