I have to say, before I go on to say anything specific, that a lot of the "criticism" so far in this thread has been based on platitudes and clichés, and not serious reflection. Now, I'm not a communist - as far as I know - but I still think it deserves better than that. Having said that...
Not to mention a simple matter of economics.. committee directed economies don't work.
Command economies do have certain advantages. The Soviet Union, for all its problems, did manage something remarkable. If you look at the numbers from the Soviet period, the growth is incredible. It did eventually stagnate, but it would be simplistic to claim that's simply inherent in a planned economy. The arms race with the United States, and the war in Afghanistan, were contributing factors. It may also have been too heavily based on heavy industry, but again, that's sort of focus is not part and parcel of a command economy.
I do want to make it clear, at this point, that I don't actually advocate a command economy. I'm also not a proponent of a pure market economy.
As to the claim that communism is simply contrary to human nature, that is ... well, you'd have to know more about human nature than I think anyone does. You'd first have to prove that there is such a thing as "human nature". Because while we, like all animals, have our evolved instincts, we also have the mental faculties to ignore those instincts and act contrary to them. What you'll find, if you dig through various theories of evolutionary psychology, is that we ignore our instincts and our evolutionary heritage, shall we say, quite often.
If saying that communism is contrary to human nature is a sufficient argument, that leaves us in the unfortunate position of possibly having to accept racism and sexism on the same basis. I'm not, in other words, denying that we are, first and foremost, concerned with our own well-being as opposed to that of people around us ( certainly outside our immediate group, who may be necessary to our survival ), but rather that the record shows that we're capable of ignoring this supposed human nature, and if it can be done in some cases, it can be done in all cases.
Communism fails not because some want more then others but because those who are incompatible with said society must be removed.
Perfect communism does not tolerate laziness, everyone has to do their "fair share" in Capitalism you can be lazy, and you simply must deal with certain economic setbacks.
Perfect communism cannot handle individuals with diseases, those unable to work, they are a drain and must be removed. Capitalism does the same, but because resources are left in the hands of the individual, you can use YOUR resources to aid those people and care for them. Capitalism is pure and instinctual communism will always be a failed experiment it has NO future.
What you said is completely contrary to the communist ideal
of "from each according to his ability, to each according to his need". This, I think, is predicated on the assumption that most people, if given the choice between working and being idle, will choose work. I think, furthermore, that this view is correct, as I think anyone who's gone without work for a long time will agree.