About the whole communism thing... I don't know, personally I think people are too hung up on political systems. There can be oppression under communism and oppression under capitalism and oppression under monarchy and oppression under socialism. Basically anywhere power is held by a small group that doesn't have to answer to anyone, that believes they are above the law, that prevents free speech and criticism of government policy, that prevents the populace from having a real say in government, that's oppression. A system without proper checks and balances, where the government doesn't have to answer to the public will result in oppression. When people in government place money and power above their care for the citizens who look to them for fairness, it's bad news. Whenever leaders forget the human element of the equation, the people get screwed.
I actually think that a type of communism can work, especially on a small scale, but Marx is a bit unrealistic about some things and a lot of bad things have happened in the name of communism that people freak about whenever anyone mentions it. I think the world is struggling to find a sustainable and people-friendly economic model right now, because what we've got seems to be malfunctioning. I think some communist ideas are worth a second glance. It's sort of like the bible, I mean some good ideas, some bad, it's just people need to use their own critical thinking and good sense to figure out what's for them and what's stupid and people would just rather follow a leader than think it all out for themselves.
I think sharing can work in a small group where you know everyone you're sharing with and know they'll kick back to you in time or they'll be in trouble. Problem is when there are so many people and society is impersonal. It is easy to screw over an organisation like the IRS because it is not personal and doesn't really make you feel guilty. This impersonal aspect makes people not want to share because you don't know who you're sharing with and what they're doing with the money and if they're sharing in the work or what. With a small group of people where everyone can be held accountable, (in a family for example or among a group of close friends where there is trust between people) communism works. With millions of people it can't work because we can't trust millions of strangers to share with us.