This chapter examines advertising and social media in order to further understand the character of online audiences’ productive activity. Considering theorizations of free labor and the audience commodity, we argue that commodification is at the core of capital accumulation strategies on social media sites. Users play a dual role in this process: as a source of free labor and as providers of personal information that is collected and used in the process of profit generation. This reveals a double process of commodification at work on social media sites and reflects larger patterns of capitalist exploitation, under which general social relations are increasingly becoming productive.