We need an alternative to commercial social networks. These have grown immensely in power in the last decade. In the process, they have been monopolizing all aspects of communication within our society - as they intermediate more and more of social, civic and cultural ties. The risks to public space associated with this process are much larger than those diagnosed with the rise of web portals in the 90s (whose role was often compared to shopping malls that have been destroying public spaces in our towns and cities). There are interesting attempts to regulate these services, for example by providing data and content interoperability and adequate protection of privacy. Yet the real challenge lies in developing institutional frameworks for providing these services as networked public infrastructure.