Recently, there has been a significant growth in the science of networks, as well as a big boom in social networking sites (SNS), which has arguably had a great impact on multiple aspects of everyday life. Since the beginnings of the World Wide Web, another fast-growing field has been that of recommender systems (RS), which has furthermore had a proven record of immediate financial importance, given that a well-targeted online recommendation often translates into an actual purchase. Although in their beginnings, both SNSs as well as RSs had largely separate paths as well as communities of researchers dealing with them, recently the almost immediate synergies arising from bringing the two together have started to become apparent in a number of real-world systems. However, this is just the beginning; multiple potentially beneficial mutual synergies remain to be explored. In this chapter, after introducing the two fields, we will provide a survey of their existing interaction, as well as a forward-looking view on their potential future.