An important element of anarchism is voluntary cooperation. As with "authority", I think it's useful to examine precisely what we mean or could rationally mean by this term.
It seems clear that under modern economic circumstances, there's a substantial material benefit to cooperation. No individual can create all the material stuff she needs to live a "good life". Other people made the house I live in; other people grow the food I eat, other people built the electric generators and other people operate them to provide the electricity I use, etc. Furthermore, regardless of the infrastructure, very few of the material things we can create today can be created by just one person working alone. We have created a world full of "irreducible" complexity (which we know can evolve through the use of scaffolding).
This is, of course, an observation about present day economic realities. There's nothing in the "deep structure" of reality that logically or ineluctably requires cooperation. It seems entirely plausible that we could develop the technological and social infrastructure that would make individuals truly self-sufficient, without requiring self-sufficient individuals to live in material poverty. We do not, however, have that level of technology today.
One of the biggest ideological differences between left-wing anarchists (libertarian socialists) and right-wing "anarchists" (Randians, anarcho-capitalists, big-ell Libertarians) is how they view economic or physical necessity. Right-wing anarchists see economic necessity as being inherently non-coercive; and if someone through some circumstances can leverage or employ economic necessity to interfere with the will of another individual, they are still not "coercing" that individual. Left-wing anarchists see economic necessity as genuinely coercive, at least in some sense.
I agree with the left-wing anarchists: economic necessity is coercive, and someone who leverages economic necessity is himself coercing others. "Work for me or starve" is just as coercive as, "Work for me or I'll kill you." I disagree with left-wing anarchists, though, in that I see economic coercion as being a part of present-day physical reality; economic coercion is not a purely social construction. Our social constructions do not establish but rather manage and distribute (or concentrate) coercion by economic necessity.
Just as we don't have true freedom of religion unless we have the freedom to adhere to no religion at all, we don't have voluntary cooperation unless we have the freedom to not cooperate at all. And we must have the freedom not just to survive, but to live a "good" life without any social cooperation at all. But noncooperation is simply not physically possible today, and without the physical possibility of noncooperation, we cannot have voluntary cooperation. We're just arguing over what kind of involuntary cooperation we want.
As I see it, the social constructions around economic necessity differentiate anarchists, "socialists" and communists. Anarchists seem to more-or-less want to wish away or socially-construct away economic necessity. You cannot, however, wish away reality; you have to work to change it. Socialists want to equitably distribute economic necessity (or, rather, equitably distribute capital, the means to respond to it). But capital, under today's circumstances, must be concentrated to be effective. Since workers must cooperate to concentrate capital, noncooperation is untenable, and we do not have voluntary cooperation.
The communist solution is to socialize the concentration of capital, in much the same sense that we socialize the concentration of directly coercive power in the hands of a more-or-less (and presently less rather than more) democratically elected government.
Must as I completely agree with anarchists that society of autonomous individuals more-or-less immune to organized coercion is desirable, we can't just declare an autonomous society. We must instead create a bridge to such a society. The specific set of social constructions we call "capitalism" cannot form such a bridge, not because it concentrates capital, but because it concentrates capital in the hands of private individuals, and almost forces those individuals to use that capital for their own individual benefit, without regard to mutual benefit.
Communism means, and has meant since Marx, to do the best we can with what we have today to build such a bridge: a bridge from a society dominated by economic and physical necessity to one dominated by each individual's self-actualization. To the extent that historical communist governments did not build such a bridge, they failed at the task I would have set for them, and at the task that Marx set for them. We can talk all we want about why they failed (did they jump or were they pushed?) but lack of success for any reason is failure.
But failure is not necessarily thorough discredit. The accomplishments of historical communist governments are notable and dramatic, and we can plausibly attribute their failures to circumstances external or accidental. The nascent Soviet Union first faced a bitter "civil" war openly backed and supported by the West, followed by the explicitly genocidal Nazi regime, followed by the implacable hostility of a nuclear-armed United States. And neither Russia nor China suffered through the century of armed conflict that established what few "Enlightenment" values that became part of the West's common social construction (and the West seemed willing and easily able to abandon those values in their relation to their colonies, leading to excesses as gross as the Belgian Free State, or the less malevolent but still socially distorting colonization of India).
It's not by any means a perfect or optimal solution, but communism still seems to be the best we can do presently to build an economic and social system that will indeed lead to the development of an autonomous society.