While we all someday dream of a perfect system that will fix a lot of the problems in the world, the reality is that its not that simple. Communism is one such system that spans from discontent with the current and overwhelmingly popular system.
Communism stems from that issue of class struggle and the accumulation of wealth by a minority that usually gets grouped under the title 'The Elite' or the landowners. While I may have a limited knowledge on Communism one thing I do know is that Soviet Communism isn't real Communism and that there are many interpretations of what it truly is.
Communism in my mind features a system whereby companies are owned by the employees who run them with everyone having an equal stake. From what I've also read, Communism doesn't involve a state as such. This way everyone who works gets their fair share of the profits that can be taken or chosen to reinvest in their own business. I'm sure it's a lot more complicated than this but lets keep it simple for the moment.
The problem to me lies in the fact that humans are actually animals (yes really) and have base instincts that involve competition and as Mr Bawa said, Survival of the Fittest. Because of this someone somewhere will always try to get more power or wealth, thereby breaking the system down. Ideally this won't happen, but it most likely will unless people rise beyond their normal behaviour.
I back this up with an example of sorts. In an ideal scenario a totalitarian regime ruled by one honest man is the ideal system. This one individual can decide what is best for everyone and carry it out without opposition. This too rarely happens, and corruption of the person eventually takes places, or failing that, the individual dies leaving a vacuum. The person or entity that fills the vacuum rarely shares the same exact ideology.
To me it all lies with the people. If they're willing to rise above their base instincts then an ideal system can be implemented. The problem is not the system itself, but the people in the system, which is basically each and everyone of us. We like to lay blame on politicians for wrecking everything, but we too play a part by our own actions in some small way that accumulates as each individual performs similar actions.
Almost every socialist orientated person I've ever met counters all kinds of problem with some kind of state control to stop people from taking counter productive actions to the system. But then there's the problem again, what keeps the state in line? If we were all self governed and truly set on a proper course, then practically any system would work without being abused; the problem is we aren't there yet. Thus every 'noble' and 'fair' system tends to fall apart somewhere down the line.
Power lies in the masses... the problem is, they are not enlightened people in the majority of the World. We always have movements, but lead by one person. The body of the movement, the masses cannot think for themselves. There lies the problem...
Imagine a world where every individual was a powerful, self functioning and fully knowledgeable person... would we stand for the hypocrisies of or leaders then? Would we stand around while a system was being abused? You tell me...