mutually consenting self-organization (even if it has a hierarchy). . .what's the issue? I have a company, so I hire you. I am the owner, and you are the employee. You are free to leave and I am free to fire you (unless we've entered into contractual agreement otherwise). *fails to see the problem*
Canarchy like communism 'hopes' that no subset of the population forms an organization, and becomes powerful enough to enslave the rest. To make it more simple; what stops an organization becoming so powerful that it can use coercion to enslave the rest ?