F.A. Hayek's "The Road To Serfdom"
“Our freedom of choice in a competitive society rests on the fact that, if one person refuses to satisfy our wishes, we can turn to another. But if we face a monopolist we are at his absolute mercy. And an authority directing the whole economic system of the country would be the most powerful monopolist conceivable…it would have complete power to decide what we are to be given and on what terms. It would not only decide what commodities and services were to be available and in what quantities; it would be able to direct their distributions between persons to any degree it liked.”