Contemporary mobilizations are largely enabled by and modelled after commercial social media platforms. The materiality of the communication infrastructure thus plays an important role in determining how people mobilize, organize and strategize. This chapter explores the tension between activist agency and the structure and political economy of platforms through the lenses of the cloud. The cloud is a) a metaphor for a particular way of connecting individuals in an instance of collective action, and b) the virtual imagined space hosting and shaping individual and collective interactions and meaning-making activities, constituting the repository of soft resources (e.g., identities, frames, etc.) critical to collective action. Talking about the cloud allows us to move beyond the specifics of individual platforms such as Facebook and Twitter, addressing social media as a whole rather than separate services. Disentangling the materiality of the cloud will help us understand how infrastructures shape activists’ tactics, identities and networking strategies.