Concerns about privacy and personal identity impede use of data about genomic variation, phenotypes, demographics, and exposures from large numbers of people to uncover the contributions of such information on health and disease, knowledge that can improve clinical care. People worry that these data and genomic data in particular, cannot be secured. Many fear that data about them will be used in ways they oppose (e.g., to deny them and those they love access to jobs and insurance) because existing legal rules about such uses are not comprehensive.