Internet and social media research has created new methodological opportunities for educational and social sciences, but also new ethical challenges. In many ways, current research ethics guidelines and legislation are still limited and provisional. In this chapter, we address ethical considerations emerging from a research project based on a Facebook study as an empirical case. The data material is based on large-scale computational material from a thematic teacher professionals Facebook group of 13,000 members over a three-year period, combined with ethnographic observations and detailed interaction analyses. We exemplify our approach of a "situated ethics" where the relation between analytical focus, methods, participants as well as technological platform contingently and inductively is considered throughout the research process. Ethical considerations around privacy, anonymisation and informed consent are examined and also discussed in relation to the biases and conditions of the Facebook platform. We also highlight issues arising from the particular intertwining of emerging computational approaches with those of education and adaptations of established interactional methods for social media research. We also discuss the potential risks of causing professional and individual harm to teachers by this type of research. [For the complete volume, "Designs for Experimentation and Inquiry: Approaching Learning and Knowing in Digital Transformation. New Perspectives on Learning and Instruction," see ED661573.]