Blocked exchanges revisited

This paper reconsiders the topic of blocked exchanges. It has been argued by some philosophers and social theorists that in order to encourage people to make donations of, e.g., blood, the sale of such items should be banned by law or public policy. In this paper I argue that (a) donations made without the option of selling are morally diminished and (2) selling such items isn't morally wrong or even insignificant in all cases since prudence (which is a moral virtue, pace Kant) may require that one sell them.