In the long view, modern history is the story of increasing rights of control over your body – for instance, in matters of reproduction, sex, where you live and whom you marry. Medical experimentation is supposed to be following the same historical trend – increasing rights of autonomy for those whose bodies are used for research.
Indeed, the Nuremberg Code, the founding document of modern medical research ethics developed after the Second World War in response to Nazi medical experiments, stated unequivocally that the voluntary, informed consent of the human subject is essential. Every research ethics code since then has incorporated this most fundamental principle. Exceptions to this rule are supposed to be truly exceptional.