This document summarizes the challenges of sharing data on the internet in a legally and technically interoperable way. It discusses how social and legal issues like licensing, attribution, and copyright impact data sharing. It argues that an integrated approach is needed that makes sharing easy, legal and scalable through building infrastructure, using open standards, and treating data as a network resource rather than intellectual property. Norms and terms of use may be better than licenses to promote sharing while avoiding restrictions that limit downstream use and interoperability.