This study examined the ethical considerations researchers have made when investigating MOOC learners' and teachers' Twitter activity. In so doing, it sought to addresses the lack of an evidence-based understanding of the ethical implications of research into Twitter as a site of teaching and learning. Through an analysis of 31 studies, we present a mapping of the ethical practices of researchers in this area. We identified potential ethical issues and concerns that have arisen. Our main contribution is to seek to challenge researchers to engage critically with ethical issues and, hence, develop their own understanding of ethically appropriate approaches. To this end, we also reflected and reported on our own evolving practice.