It always seems people, indeed, relate communism with Marx. I really think communism as a principle is simply to contribute with what you can to the community, selflessly. In other words, the community's benefit, and well-being is number one. In my opinion, IF this was to be applied as i've just defined it, that community would be better economically, and socially, than any other community based on whatever political system.
Greed is what prevents communism (not necessarily Marx's) from working. Apply it purely, and it'll work perfectly; then again, who would do so?
In short, people who argued here for communism, brought-up good examples, and good points. People who argued against it, just don't know what it's all about, and actually just see USSR and its EPIC fail, and China's hypocrisy.