It may seem irreverent to ask, why democracy? So be it. We should take nothing for granted, and we might learn something from the Anarchists, here. After all, democracy means that the minority defer to the majority. An Anarchist is not willing to defer to anybody. Why should anyone who values freedom, as Anarchists do, support democracy?
Something of the same case can be made for democracy as we have made for narrow voluntarism. Even in voluntary organizations (given the circumstances that people face that lead them to accept domination as a necessary evil), some opportunities will exist for little dictators to accumulate power and dominate people. Democracy puts limits on that opportunity, and we need all the limits we can get. In Hirschman's terms, both exit and voice are necessary to limit power.
And, of course, democracy is particularly important in governments, since governments cannot be voluntary. But democracy is doubly essential within productive organizations, where it is most conspicuously absent in our capitalist "democracy." Here is the reason why democracy is particularly important in productive organizations: in production, it is unavoidable that one person will often be required to direct the labor of others. Essential as this relationship of direction is, direction and domination are very close. Direction will become domination unless the director is responsible to those whom she directs. This responsibility to those directed is direct democracy -- the director must be elected by those over whom she exercises direction. If she is not, domination is the inevitable result of the direction of labor.
It is interesting that in our "capitalist democracy," democracy is limited to the political realm, and strictly excluded from the productive organizations. Why? Because democracy in the election of Congress and of the officers of the Rotary Club does not threaten the power of the ruling class. But democracy in the productive organizations does threaten that power. Democracy is our ideal -- as long as it doesn't threaten the power of the employing class. That's ideology. And the ideology is strikingly similar to that of the defunct Soviet Union. They were all for democracy, too -- they had a different concept of democracy, of course, one that I regard as cockeyed -- but even that sort of democracy was not to be allowed in the workplace. There, it was one-man management. Ideology.
That is why productive organizations should be both democratic and voluntary, that is, they should be worker cooperatives.