This was tried and failed in Republican Spain prior and during the Civil War.
First of all, this should be moved to Chat, given it is not a discussion about the possibilities and effects of a lasting, RL example of anarchist communist society, but a discussion about how people would eat each other if such a thing happens.
Second, the experience failed during the SCW failed because the republicans first, and the nationalists later, put an end to it. According to the testimonies, society was fairly functinal during the Spanish Revolution. And I still think Spain was the best shot for an anarchist experiment, though I can't figure out a decent, definite POD.
Now... Let's not forget what an anarcho-communist society is: A direct democracy in which people decide about everything, including the means of production. The learnt lessons regarding communism don't apply here, for an economic democracy has much more potential for succeeding than a central planning. Its ethos is much much closer to that of Athenian democracy than anything else, except for the universal participation, and (here is the great problem), the lawlessness.
I don't think societies disintegrate without a good reason, and I think that, if both the society and the ones who have coertitive power (let's not forget the anarchist experience included a fair deal of militiamen) accept the legitimacy of a set of rules (anarchism, let's sing along,
has rules), then the rules are into effect by all extents... but I also think that, by removing law, anarchist societies would remove themselves from the main prevention from arbitrary coertion. Let's not forget that law isn't there only for setting the rules of coertion, but also for putting the limits between an acceptable and an unnaceptable coertion. Of course, this is the liberal lecture on law, not the anarchist one, for which every rule is a form of aggression, but such a lecture owes everything to the Enlightement's dream of a primigeny lost paradise of natural justice and unstained, compassive men, corrupted by the original sin of private property... which is
fucking hilarious.
An anarchist society wouldnt be one of warlordism and poverty, but one of something more subtle. I would be a society in which your neighbours would look bad on you if you don't participate or you don't do it according to what is perceived as the greater good, or just if the woman next door likes to go to bed with you rather than with the others (even in the hippie communes, sexual intercourse was an act of exclusion); and in which the charisma would be the only possible key of success; in which if you are not a liked person, people could (democratically, horizontally, after a fair trial) vote you from being expelled, or killed of tortured (yeah, yeah, there is an ideal of fraternity, but ideals have a most curious tendency to rot after a generation).
And anarchist society, rather than looking like a war-torn feudalism, would look like a secondary school. With blue collars, and without fucking restraint.