Social networking sites are highly popular and have profoundly changed the way people, including educators, communicate and interact. For many teachers the use of Facebook and MySpace is seen as a valuable educational tool and an integral part of their private social interaction. However, the exponential growth in the use of social networking sites by students and teachers alike has presented new legal, ethical and professional challenges for teachers and school administrators. Teachers might argue that their social networking sites are personal websites but they are ultimately very public spaces that leave an electronic trail that can have serious, albeit unintended, consequences for teachers who breach professional codes of conduct and education laws. Teachers face the risk of censured speech, professional misconduct and possible dismissal for posting inappropriate information including comments and pictures on these websites. The purpose of this article is to examine the legal and professional risks for teachers using social networking sites and it offers suggestions that school administrators might incorporate in their policies with regard to teachers’ use of social networking sites. The first part of the article reviews relevant US cases and the second part focuses on the following legal issues – free speech, privacy and security of information, professional conduct, and the implications for teachers and school administrators in the US, Australia and New Zealand. Included in the second part are some practical recommendations for teachers and their lawyers as they develop policies addressing the use of social networking websites in the educational workplace.