It seems to me that the majority of negative opinion as to Communism is based on a 'reds under the bed' mythology - and that stemming from the USSR, most obvious real world example.
**Soviet Russia is a Limited Example**
But it IS only one example - and one, perhaps, more accuratly called SOVIET Communism - as it possessed some particular features that are, either, not universal, or actually in 'violation' of some key tenets of Communism.
Realistically, I think it would more accuratly be called a tyranny that publically ascribes to Communism.
Consider that the Gulag and shipping millions of people to Siberia, political prisonsers, etc, violate the most obvious and fundamental tenets as to 'freedom and equality'.
** Real World Examples of Success Exist**
I am reminded of a local example - which is a one of a few that I am aware - it's 'citizens' appear to be happy and healthy, and possessed of motivation and self-determination.
Which, frankly, contradicts many claims that 'Communism doesn't work' - it very clearly does.
**But it's still, Ultimately, a Pipe-dream**
As some have suggested as to human nature, a TRUE communist society, on a large scale, has yet to occur, and appears impossible - if only due to human nature.
But these aspects are just as relevant to any system, as corruption and imperialism in current democratic society shows.
Any succesful system would need to be a balance of controls, effectively to protect the citizen from other, predatory, individuals and organisations.
The obvious collapse of the Soviet Union, as it did adhere to some communist pricinples, was due to the exact same factors as any other society experiences, but magnified through it's encouragement of tyranny.
In this respect, as the USA did appear more succesful, it wasn't due to Capitalism/Communism, but to a wider sense of freedom in the US - the Russians, essentially, defeated themselves, through apathy and passive resistance.
**Communism and Libertarianism **
While at first appearing worlds apart, each is so similar - each espousing an ideal of individual rights and freedoms, but qualifying different focuses of responsibility.
Soviet Communism espoused an overwhelming individual responsibility to society.
Libertarianism espouses individual with virtually no responsibility at all.
Each presents an extreme view - and extreme positions are all most likely to lead to the degree of disfunction, then collapse, as the Soviet Union - in short, Extreme Libertarianism is as likely to succeed as Extreme Communism - that is, not likely at all, and each Utopic, in the sense that the have lovely, but unattainable ideals, due to human nature.