A Division by Zer0 explains why he thinks that human nature would not be a stumbling block for proper communism. I think he's viewing human nature with overly rose-colored glasses, and I was going to comment on his post, but my comment was getting a bit too long that I'm writing my remarks here.
Even in ancient times, it seems that humans weren't exemplars of cooperation, even though resources were freely shared. Anthropologists studying primitive cultures were surprised at the extremely high murder rate among males within a tribe, reaching something like 20%, which is a poor indicator of harmonious cooperation. And that's ignoring what they do to other tribes. At least that's what I read in Nicholas Wade's Before the Dawn, a book about human evolution, even though I might be incorrectly recalling the statistic. Even chimpanzees, a much more distant relation than our own ancestors, can get violently competitive with each other. (It may have been better if humans were more like bonobos who solve every problem through sex ...)
There's also the experimental fact that I myself have a healthy amount of laziness and a modicum of greed. And considering that I'm one of the less greedy people around me, that bodes ill for a restraint on greed for the average human nature. And of course, there's the depressingly large proportion of the human population that prefers dogma over reason ...
For communism, there are also the problems that not all things are created equal and not all jobs are equally attractive. Better quality products take more resources to build than those with poorer quality. Should there be only one single product line for any class of items? If not, who gets the better products and who gets the worse ones? Who gets to decide, and how will they decide? This sounds suspiciously like economics becoming politics. Then again, politics is a major factor on how money and resources go around, and vice versa.
There are also the essential jobs that must be done, but almost no one wants to do without some compensation. No doubt that for any job there will be people who would love to do it, but I'm pretty sure that there are far too few people who like jobs such as handling human waste. Without private compensation in some form, not enough people might be willing to do many of these essential jobs. It's hardly an insurmountable problem for communism, of course, with workarounds such as mandatory service similar to the two to three years of military service required in some countries. This does run into a converse problem of who gets what job, but it might be better than the exploitation that occurs in many countries, where people do horrible jobs with very little compensation because the other choice would be starvation.
Does this mean that I think human nature will doom any attempt at communism? Hardly. I'm rather uneasy about the vagueness of how allocation should be handled: in capitalism, resource allocation is decentralized and self-organizing, but I'm always confused about how it's supposed to work in communism. But this could be chalked up to my ignorance. Otherwise, I don't have a really strong opinion about communism.
On the other hand, I do have a rather strong opinion that an attempt at communism through violent revolution is doomed to failure. I blame history for this position. It might be arguable whether the Soviet Union or China were really communist, but they're certainly the most visible examples that ended up bad. On yet the third hand, Western nations with more socialistic policies seem to have a higher average standard of living than other Western nations. Admittedly, I'm basing this on the very small sample of the United States and the Scandinavian countries. I might also be confusing cause and effect.
If there were no scarcity of resources and all the unpleasant jobs were mechanized, I could easily see communism working out quite well. But with explosive population growth outstripping the availability of resources and a rate of automation that is still very low, I could also easily see how impractical communism might be as applied to the whole world, although I'm much less sure about it as applied to individual nations. Things might be different with much more advanced technology and population growth back under control: perhaps Karl Marx was just several centuries before his time.