 Fundamental practices of concern for direct ethical impacts on privacy include: the transfer of users’ data to third parties for intrusive purposes, especially marketing, data mining, and surveillance; the use of SNS data to train facial-recognition systems or other algorithmic tools that identify, track and profile people without their free consent; the ability of third-party applications to collect and publish user data without their permission or awareness; the dominant reliance by SNS on opaque or inadequate privacy settings; the use of ‘cookies’ to track online user activities after they have left a SNS; the abuse of social networking tools or data for stalking or harassment; widespread scraping of social media data by academic researchers for a variety of unconsented purposes; undisclosed sharing of user information or patterns of activity with government entities; and, last but not least, the tendency of SNS to foster imprudent, ill-informed or unethical information sharing practices by users, either with respect to their own personal data or data related to other persons and entities. Facebook has been a particular lightning-rod for criticism of its privacy practices (Spinello 2011, Vaidhyanathan 2018), but it is just the most visible member of a far broader and more complex network of SNS actors with access to unprecedented quantities of sensitive personal data.