This paper reviews the development of online technologies over the last 40 years in the context of the perceived risks to children. It reviews the literature on the main research, legislation and guidance and their role in the development of responses to safeguard children from the perceived threat of harm online. Significant gaps are found in the evidence base upon which effective and proportionate professional practice could be established. The paper describes the challenges presented by a rapidly changing medium, specifically the development of Web 2.0, and the diverse levels of use and creativity young people have shown in adapting it into their lives. A distinction is drawn between the developmental imperatives of risk taking in adolescence and behaviour characterized as thrill seeking, which may be indicative of vulnerability both online and offline. The paper concludes with recommendations including a refinement of safeguarding resources and practices with a greater emphasis upon young people deemed to be vulnerable online. (Contains 2 figures.)