So you implicitly suggest that all people share the same principles of life and moral values. It may be true for a small isolated group of people and your idea of ostracism and outlawry may actually work between them. But if you take some larger proportion of population and apply this principle among them you will see tensions arise and eventually you will end up with fractions denying and neglecting each other (if not fighting)...
Probably. But if they have their own spaces, like minded people will gather. They may even decide to form coercive governments. But if decentralization is common, and people have learned to be independent, those will be pockets.
But what about economics? To sustain the achieved standard of life we need that tight hierarchical integration between people (ironically called division of labor) which most anarchists loathe as much as they are afraid of...
Would you do business with someone who used slave labor?
If not, and the other people you do business with agreed this was bad, the slave owner would either need to stop owning slaves or go out of business
If so, and the other people you do business with agreed this was bad, you put yourself at risk of going out of business along with the slave owner
I won't bother with a society which believes this is good for nobody wants to be enslaved, and a society which cannot grasp something as simple as empathy surely has no capacity to survive as anarchists for long; they're too busy installing a state.
Thus, the incentive of using slave labor is killed; the last resort is to ask the state to protect your slave-owning habits, but since that can't happen in a society of rationals, for what rational seeks a guiding force but his own, it's effectively squashed and business continues as usual. Behold, ostracism.
Also: for the same reason that the rational does not need the state to dictate his actions, the rational has no need for a hierarchy of business; since every worker is equipped with the mental skills needed to run a business (it's kind of sad to note that they currently don't, despite 14 years of involuntary "education"), they can very easily form businesses together and share their wealth with each other as they see fit. What good is a corporate empire on the local level?--it's just extra overhead for the worker, who gets what's left trickled from the top of the pyramid as our current system is now, and accepts it as he cannot see any other way to make a living, nor was he provided the skills required to see why it's screwing him over (though he will constantly complain about it to his peers) thanks to the corporate empire's bed buddy, the state, where there is no incentive to produce thinking adults via the educational system, merely productive ones.