Organizations are inspired by the massive social media use in the private domain and try to filter interactions and knowledge sharing in socialmedia also for professional purposes. Even if the interest in social media isstrong in the private domain, the use is far less widespread in organizations. The trajectory of traditional information spread through web platforms into use of new and open social media platforms stresses organization's and professionals to enrich user-generated content and take part in and enhance social networking. This study explore how social media is used in organizations and how professionals´ practice is challenged by use of social media of reaching out, sharing knowledge and interaction with target groups. Through illustration of two research cases; municipality-citizens' interactions and university-industry collaborations, three affordances of social media practice are emerging; incentives, perceptions and openness, where social media is constituted as the boundary object