One of the main issue with Capitalism, is: money=power. The more money you'll have, the more power you'll be able to get. And with more power you'll get, the more you'll be likely to used it to get more money. In the end, it's nothing more than a vicious circle.
With a Communism system, the money isn't used to get power, but instead used as a tool to help the society. With no class higher or lower, it's kind of useless to try to get more, since the system don't work that way. In a unequal system, people can become jalous of the fortune of some other, this combine with greed.....it's not likely to end up well.
I'm not saying that greedy is impossible in a communist system, but less likely to happen, mainly because of the more equal share of value. In capitalism, they need to removed money from politic, this is by far the main problem we got.
PS: Speaking of money, by curiosity, just a small question to anyone who is American: Did the penny is still used and made every year in the US? I ask that since the penny was removed in Canada since....i think a year already.
Even though money is often classified as the "root of all evil," it serves as a great standard for exchange for products and services. The problem with bartering is that there is no common exchange for debt--for instance, if you had a coop of chickens and I had hogs, you could give me four chickens for one sal. But let's say someone else has a cow that I would like; unfortunately, they have enough chickens and don't want any more, but instead want tools. If I have no tools to give, I'm going to have to go find someone willing to exchange chickens for tools for a cow. Then there's the problem of how much value do you attach to each item: what if someone values chickens more than others?
In an equality system such as communism, it stifles the ability for a person to advance him/herself. For instance, let's assume that I want to live in a four bedroom house but everyone else has a two bedroom house. For the sake of argument, let's assume that the government supplies all housing (like China does). I have no motivation to work harder or exert more effort because unless the government suddenly decides to give everyone four bedroom houses, I'm still going to be stuck. It really snuffs out the idea of individuality in the name of "the common good."
And in answer to your pennies question, yes, for some reason we still have the damned things. I keep them in a jar on my desk where they collect dust.