I think TRUE communism could never work because of natural human greed.
That's like saying capitalism could never work because it's human nature to cooperate and share things with others. Just because people can be greedy doesn't mean we have to base our whole economy on rewarding the greediest people in society with tons of power and property, so they can constitute an elite that runs all our industries. That's just insane.

Communism, simply put, is a classless society, where the means of production are owned and managed directly by the people, under the principle of "from each according to his abilities, to each according to his needs". If resources are allocated properly, and people's needs and desires are fulfilled, why would people demand more than what they need to fulfill their basic needs and desires? If food is freely provided to you as long as you contribute to society according to your abilities, you're not going to hoard tons and tons of food; you'll only take enough of the food you like to get by.

A communist society would eliminate a lot of the unnecessary labor under capitalism, freeing up a lot of work power to doing actual productive work. Once private property is eliminated and bottom-up democracy replaces top-down fascism in the workplace, there will be no need for accountants, managers, CEOs, lawyers, marketers, salesmen or anything of the sort. Without a constant drive for more and more profits, we can concentrate on actually providing what is needed in society instead of trying to create as many artificial desires as possible.

Communism also implies the absence of a state. Yes, that's right, a stateless society. Communism is not absolute state control over the economy, although some communists do support state control over the economy as a transition period on the road to communism (I don't subscribe to this view however, since all past attempts at this kind of transition have failed miserably). Communism is the ultimate expression of democracy; people arranged in free associations exert direct control over social affairs in an egalitarian manner, without presidents, politicians, parliaments, police or other pesky parasites on society. If people are capable of running society for themselves, as the principle of democracy clearly implies, then there is no need for government or any type of rulers to tell us what to do. The few rotten apples who pose a threat to society can be dealt with in a democratic, egalitarian manner, by decentralized citizens' militias if need be.