I read this about a month ago on wikipedia and thought it was brilliant. It's from the Dali Llama:
I think the major flaw of the Marxist regimes is that they have placed too much emphasis on the need to destroy the ruling class, on class struggle, and this causes them to encourage hatred and to neglect compassion. Although their initial aim might have been to serve the cause of the majority, when they try to implement it all their energy is deflected into destructive activities. Once the revolution is over and the ruling class is destroyed, there is nor much left to offer the people; at this point the entire country is impoverished and unfortunately it is almost as if the initial aim were to become poor. I think that this is due to the lack of human solidarity and compassion. The principal disadvantage of such a regime is the insistence placed on hatred to the detriment of compassion.
While most critics will cite the loss of incentive as the principle problem with communism since everyone would ideally get the same amount of goods and services, which I think is a good point, I think this criticism goes further to the heart of the problem.
The Dali Llama for this reason considers himself a half Marxist. He, like most communists doesn't believe that the governments that champion Marxism really represent the system. According to him, though the implementation of Marxism has often been a disaster, Marxism itself is founded upon moral principles of equality while capitalism is based upon personal gain.
I think both systems can fail for the same reason. They both treat the human situation as primarily economic. Capitalism only works best when you have good people who will use their resources not just for themselves but for others and for the long term good. But Marxism cannot be good thoroughly as it is a godless system.
Reflecting on the Dali Llama's comment, it seems to me that Marxism has worked out as an affront to humanity itself as it flies in the face of the most important goals for humans. It stands as an outright perversion of the second greatest commandment to love one's neighbor, where in Marxism we are called to love 9 out of 10 of our neighbors (in a materialistic way) but to hate that one in 10 who has more than the others and take his possessions by force to distribute to everyone else. Of course it is explicitly Godless as well which is an affront to the most important commandment.
Of course some people see the economics of the early church as communistic. For one, they forget that communism is an explicitly Godless system, so that identification will never work out. But scripture as a whole and even the new testament more specifically doesn't completely fit these descriptions of communism nor capitalism. There is an instance in acts where many in the early church held goods in common, but at the same time, there were other churches where Paul encouraged those who were able to support widows to do so thus the church would be able to use its resources in other ways. Clearly the implication is that people had funds that were their own.
The point here is taking care of one's neighbors, but there's no way to do that set in stone.
But what else could we say of scriptural economics. On the one hand, there is the parable of the vineyard owner who paid everyone a denarius no matter when they came to work demonstrating that the vineyard owner paid each according to their need. Of course it is emphasized that the owner and workers freely entered this relationship. On the other, the parable of the talents shows a king who rewards hard work by giving more power to the most successful servants. And there were those churches were people held goods in common. What we have here is meritocracy, rulership by the most competent and most successful and privatized socialism. No majority put it to a vote to force the wealthy to give up their wealth and there certainly was no bloody revolution. We do not see nameless faceless bureaucracies doling out checks and food stamps to people with no relationship of gratitude. People of their own free will and their own resources took care of each other.