The emergence of social media has in many ways changed how individuals interact, communicate and also consume online. Due to the massive, world wide use of social media, organizations are starting to use social media in order to be present where their customers are. Earlier research has studied social media from different, rather fragmented perspectives such as social media use for marketingor for internal communication. However, research on the organizational implications and challenges from a more general organizational social media use is lacking. This thesis explores organizational implications and challenges of social media use over time. Hence the focus lies on both internal and external organizational activities related to social media use. The consequences of social media have been particularly striking in service industries, e.g. banks, restaurants and travel agencies. Social media has fundamentally changed how we (can) buy services, and also how service is provided. For example, we can ask a question or make a complaint directly on a specific social media platform. Hence, social media have had implications for the relationship between service organizations and their customers and thus changed the context in which service is delivered and experienced. The service encounter, i.e., the actual meeting between the customer and employees, has come to take place on social media platforms. The expansion of social media has affected the hotel industry in several ways. Hotel guests are using social media platforms in order to review and share experiences about hotels, and hotel organizations use social media to keep up with competitors and customer demands. The aim of this thesis is to describe and understand the challenges social media use brings to organizations in the service industry, inparticular hotel organizations. The following research question is addressed:Why and how does the use of social media platforms represent organizational challenges? The empirical data focuses on the introduction and use of social media in one international hotel chain over a four-year period. Furthermore, data was collected from other, independent hotels. The empirical data was collected through interviews, online observations, workplace observations and written documents. VIIIA multifaceted theoretical framework was used, including the Technology-Organization-Environment framework, the concept of technological frames, andthe concepts of functional simplification and closure. These theoretical frameworks capture the drivers behind organizational social media use and how individual employees interpret and use social media, but also how social media attributes create the need for new organizational routines and management of social media content created outside organizational boundaries.The analysis illustrates how social media use creates challenges for the studied organizations. Five main organizational challenges have been identified: the nature of social media versus organizational structure: how organizations and individuals make sense of social media over time; how private use of social mediahas implications for professional use; how social media creates stretched service encounters; and pseudo-relationships and roboticization of service