There is considerable interest in biodiversity prospecting (the search for valuable new products from natural sources) as a conservation strategy. In an earlier paper, we have argued that the value of the marginal species (and, by extension, the incentives for the conservation of the habitat on which it is found) is small. In this paper, we show that investments in biodiversity prospecting are unlikely to increase incentives for conservation by much. If the value of the marginal species were appreciable, researchers ought already to have made investments to exploit it. If it is not, it is doubtful that additional investments will generate any substantial increase. It is important to be clear about our findings: we are not saying that none of the myriad uses of biodiversity is important. Quite to the contrary, we are saying that if biodiversity is important, more effective strategies for its conservation must be found.