The ‘sharing economy’ has become a new buzzword in urban life as digital technology companies set up online platforms to link together people and un- or underutilised assets with those seeking to rent them for short periods of time. While cloaked under the rhetoric of ‘sharing’, the exchanges they foster are usually profit-driven. These economic activities are having profound impacts on urban environments as they disrupt traditional forms of hospitality, transport, service industry and housing. While critical debates have focused on the challenges that sharing economy activities bring to existing labour and economic practices, it is necessary to acknowledge that they also have increasingly significant impacts on planning policy and urban governance. Using the case of Airbnb in London, this article looks at how these sharing or platform economy companies are involved in encouraging governments to change existing regulations, in this case by deregulating short-term letting. This has important implications for planning enforcement. We examine how the challenges around obtaining data to enforce new regulations are being addressed by local councils who struggle to balance corporate interests with public good. Finally, we address proposals for using algorithms and big data as means of urban governance and argue that the schism between regulation and enforcement is opening up new digitally mediated spaces of informal practices in cities.