Medical breakthroughs owe their existence to the human subjects who volunteer for studies. Federal and international regulations aim to assure that research on human subjects is ethical—that the potential benefits outweigh the risks, for example, and that subjects give written informed consent. But recent trends may be loosening the safety net.

The number of trials has skyrocketed in recent years, straining the oversight system and putting pressure on researchers to recruit more subjects than ever before. In addition, whereas trials used to be conducted mainly at academic institutions, most are now run by for-profit companies, which often pay doctors to sign up volunteers and pay review boards to approve the trials. These arrangements raise concerns about financial conflicts of interest.