With the proliferation of digital signage in the retail environment and the simultaneous rise in social networks, a new opportunity presents itself to show social network comments in stores. This chapter provides an overview of social networks and its relation to word of mouth marketing and will then apply these concepts to the role of social networking in advertising and retailing, particularly focusing on digital signage. Further, a case study of an experiment is presented where a chain of small-space retail stores measured the sales data in a controlled field study. This chapter will show that stores with digital signage displaying comments from social networks were able to increase sales, though not as much as those showing traditional advertising. Additionally, the data revealed that displaying product-specific social network comments a more effective than showing general brand-related comments. The chapter concludes with recommendations for placing social network comments on digital signage.