In the last 25 years writing in bioethics, particularly in medical ethics, has generally claimed that action is ethically acceptable only if it receives informed consent from those affected. However, informed consent provides only limited justification, and may provide even less as new information technologies are used to store and handle personal data, including personal genetic data. The central philosophical weakness of relying on informed consent procedures for ethical justification is that consent is a propositional attitude, so referentially opaque: consent (...) is given to specific propositions describing limited aspects of a situation, and does not transfer even to closely related propositions. Assembling genetic data in databases creates additional difficulties for ethical justification. This is not because genetic information is intrinsically exceptional, but because the merger of genetic and information technologies make it possible to assemble massive quantities of complex information that defeat individuals' best efforts to grasp what is at stake, or to give or withhold informed consent. The future agenda for bioethics will need to take account of both these limitations of appeals to informed consent. (shrink)