Crowdfunding offers a different approach to social innovation undertakings at a time of rapidly shrinking state support. Social innovation involves new social practices that aim to better meet the social needs and shape collective futures. The innovation here hinges on the way in which crowdfunding platforms can change the way that society works as well as the financial details of individual campaigns. Working alongside the design features of the platform are the social, economic, and legal aspects of financial systems that evolve over time and shape what platforms can enable. In this chapter, we discuss how publics form around platforms with an interest in what is being supported. We use the term “paying publics” to refer to the way in which the four UK-based platforms we feature are using this relationship with their funders and supporters to change how funding affects communities and environmental behaviour. We can be quite precise about who the individual members of a crowd contributing through a particular platform to a specific campaign might be, whether friends and family or international networks of backers. So, we suggest that we are not served well by the term “crowd.” In talking about publics, we refer to the way that particular groups may be brought into being by the actions of the platform. No single platform is redesigning economic life. However, each offers possibilities for linking private, public, and personal money and services in new ways; together, that signals societal as well as financial innovation. New common interests grow around the platform and can take on a life of their own.