At a macro level, with communism, the state will inevitably fail to predict the correct demand for products and the result will be that a black market will rise

At a macro level, with communism, the state will inevitably fail to predict the correct demand for products and the result will be that a black market will rise for products with more demand than supply and the wasteful destruction/dumping of products with more supply than demand. The rise of black markets in particular will ultimately undermine the communist's promise of "to each according to their need". Almost all modern communistic systems are actually mixed economic systems reflecting that a pure communistic model is not feasible. At a micro level, communism saps the entrepreneurial energy from economies as it relies on the state to determine what goods and services should be produced. It also potentially acts like a disincentive to work as work is performed for the national well-being not the personal well-being. Not that all individuals reject the notion of patriotic work for the betterment of the nation but I feel that more are incentivized by personal rather than patriotic rewards. Traditionally, communism leads to the restriction of movement and voice for the citizenry. Any system that needs to erect laws and walls to keep its own citizens from leaving or voicing their displeasure seems to be a system that is fundamentally flawed. I am not saying that any other "pure" ideology (particularly free market capitalism) is without faults, but you asked specifically about faults related to communism.