While social media data is increasingly used in new media research, it is still quite novel for the design discipline, especially in the field of participatory design. This chapter explores how social media data can inform designers about the social layer of a local context before they enter the design stage (whether it concerns designing a game, an intervention, a service or any other type of design) and even before they enter the participatory process. This chapter aims to uncover the potentials of social media data for the design profession, with a particular focus on designs that aim for on-going community participation in public space. Finally, this chapter proposes an approach for analysing social media data to discover potential user groups that can act as local agents in appropriating and prolonging the life of the design project. By deconstructing an existing design project that uses digital media as a tool for citizen empowerment, and by introducing various case studies that work with social media data, this chapter aims to present several potentially valuable resources of user data for designers.