Young people are growing up in a ubiquitous 24/7 digital media environment, where mobile devices, social networks, interactive games, and online video have become ingrained in their personal and social lives. Now the forces of Big Data are further transforming that environment, ushering in a new generation of sophisticated analytics and measurement systems, and facilitating the growth of unprecedented profiling and targeting. Data can now be collected across a spectrum of technologies that children encounter—at home, at school, at play, and in their social interactions. These trends pose serious threats to children’s privacy, raising the specter of “digital dossiers” that could follow young people into adulthood, affecting their access to education, employment, health care, and financial services. While there are regulations in place – including the federal Children’s Online Privacy Protection Act (COPPA) – that provide some safeguards for children under 13, emerging practices in the Big Data era raise a number of issues that need to be addressed by researchers, advocates, and policymakers. There are currently no laws to protect the privacy of teenagers, even though they are among the most avid users of digital media. Unfortunately, academic research continues to lag far behind the rapid changes in media and technology. Scholarly studies have explored issues such as young peoples’ attitudes about online privacy and their use of social media privacy policies, but the entire area of digital marketing and data collection remains under-researched.