I think it is a bit disingenuous for communism's apologists to dismiss the tragic Soviet experience as not being "true" socialism or communism. State terror, trampling of individual liberties, suppression of political opposition, and emergence of a privileged class of apparatchiks, while not monopolies of communist governments, have been their nearly ubiquitous concomitants. Leaving aside intentional inflictions of human suffering, the backasswards agricultural "reforms" imposed by communist governments produced some of the worst famines in history (e.g., Soviet famine of 1932-33; Chinese "Great Leap Forward" famine of 1958-1961 [est. deaths between 20 and 45 millions]) Even today, famine places in clear relief the differences between the quality of life enjoyed by the people of North Korea and that of their capitalist brothers and sisters to the south. The replacement of command economies with market based ones in so many countries over the last thirty years can only be understood as the product of experience, rather than of ideology.
I am not a small government or laissez-faire ideologue by any means, and do not oppose government intervention in the economy where necessary to avoid widespread privation. However, on the record, I think the rebuttable presumption must be that nationalization of economic resources is, at best, less conducive to human happiness than private ownership and operation.