Some weaknesses of communism are that it removes the price system, eliminates incentives, reduces prosperity and severely restricts personal freedom. Communism was once a dominant economic system, but as of 2014, it has been largely discredited.
Communism, unlike capitalism, eliminates the price system as a means for allocating scarce resources. Under capitalism, buyers and sellers rely on a mutually agreed-upon price when exchanging goods and determining production levels. In a communist economy, however, the state determines what and how much is to be produced. This invariably leads to shortages of some goods and surpluses of others. Neither shortages nor surpluses are economically desirable.
Communism also eliminates incentives. People are motivated by incentives: workers by salaries and wages and owners by profits. Because the government controls production, there is no incentive to work harder to achieve higher wages, nor is there any incentive to undertake the entrepreneurial risks necessary to earn profit. Therefore, economic activity stagnates.
A stagnant economy leads to decreased prosperity for society. Technological advances cease as industry uses inferior methods. The result is decaying industry and infrastructure and a poorer society overall.
Finally, communism reduces personal freedom. To meet prescribed production goals, the citizens of a communist regime are forced to follow government mandates. Travel into and out of the country is severely restricted and political dissent is suppressed by militaristic police.