On October 29, 2014, a British mental health charity called Samaritans launched “Radar,” a mobile app to assist individuals in severe emotional distress.1 Aimed at users of the social media website Twitter, the app scanned a person’s network for member postings that indicated signs of depression or suicide and would alert the user to contact any potentially concerning member. Samaritans hoped this would turn social networks into “safety nets,” but to their surprise, the app generated uproar over questions of privacy and potential targeting of vulnerable individuals, and the app was shut down 9 days after launch.1