Privacy online is an increasingly popular field of study, yet it remains poorly defined. "Privacy" itself is a word that changes according to location, context, and culture. Additionally, the Web is a vast landscape of specialized sites and activities that may only apply to a minority of users—making defining widely shared privacy concerns difficult. Likewise, as technologies and services proliferate, the line between on- and offline is increasingly blurred. Researchers attempting to make sense of this rapidly changing environment are frequently stymied by such factors. Therefore, the ideal object of study is one that is inherently sensitive in nature, applies to the majority of users, and readily lends itself to analysis. The study of health privacy on the Web meets all of these criteria.