The problem with communism is it assumes everyone wants that same thing. There are some evil baddies that don't give a shit about anyone but themselves. They only care about the money and the power and are usually the ones that eventually become the leaders.
If someone can tell me of an actual communist country that has worked, I'm all ears. I'm sure you could do it on a small scale, because you can weed out the baddies. On a large scale though? The greeds will take over just like anything else.