Adoption studies of social media use by clinicians were systematically reviewed, up to July 26th, 2011, to determine the extent of adoption and highlight trends in institutional responses. This search led to 370 articles, of which 50 were selected for review, including 15 adoption surveys. The definition of social media is evolving rapidly; the authors define it broadly to include social networks and group-curated reference sites such as Wikipedia. Facebook accounts are very common among health science students (64-96%) and less so for professional clinicians (13-47%). Adoption rates have increased sharply in the past 4 years. Wikipedia is widely used as a reference tool. Attempts at incorporating social media into clinical training have met with mixed success. Posting of unprofessional content and breaches of patient confidentiality, especially by students, are not uncommon and have prompted calls for social media guidelines.