This study examines the impact of social media activism in the form of a boycott case through the analysis of online and mass media news articles. The article reviews a conflict between a supermarket chain and its Estonian customers in April 2010, and focuses on definition hegemony (the process by which the crisis is defined), the reaction of journalists and consumers to the case, and its impact on a company’s crisis communication. It examines the role of social media in formenting a crisis and keeping it active. The analysis of social media and mass media texts, as well as press releases, suggest that citizens have power over corporations because of their ability to raise questions, be critical of company behavior, and in defining the crisis narrative. The findings indicate that who is able to define the crisis can significantly affect its course.