Concepts of the sharing economy are gaining traction in retail, finance, business and law. What has it to do with architecture? We examine the sharing economy's basis in peer-to-peer exchange, and its relationship with the intriguing technology known as the ‘blockchain.’ We look critically as the practical applications of the technology to architecture in areas such as the exchange of digital assets and the automation of certain types of contracts, as well as the metaphors about the city it brings to light as a stimulus to design.