Truth is for sale today, some critics claim. The increased commodification of science corrupts it, scientific fraud is rampant and the age-old trust in science is shattered. This cynical view, although gaining in prominence, does not explain very well the surprising motivation and integrity that is still central to the scientific life. Although scientific knowledge becomes more and more treated as a commodity or as a product that is for sale, a central part of academic scientific practice is still organized according to different principles. In this paper, I critically analyze alternative models for understanding the organization of knowledge, such as the idea of the scientific commons and the gift economy of science. After weighing the diverse positive and negative aspects of free market economies of science and gift economies of science, a commons structured as a gift economy seems best suited to preserve and take advantage of the specific character of scientific knowledge. Furthermore, commons and gift economies promote the rich social texture that is important for supporting central norms of science. Some of these basic norms might break down if the gift character of science is lost. To conclude, I consider the possibility and desirability of hybrid economies of academic science, which combine aspects of gift economies and free market economies. The aim of this paper is to gain a better understanding of these deeper structural challenges faced by science policy. Such theoretical reflections should eventually assist us in formulating new policy guidelines.