Large-scale software engineering requires many teams to collaborate together to create software products. The problems these teams suffer trying to coordinate their joint work can be addressed through tools inspired by social networking. Social networking tools help people to more easily discover and more efficiently maintain relationships than is feasible using one-to-one or face-to-face interactions. Applying these ideas to the software domain requires new kinds and combinations of software program and process analyses that overcome intrinsic limitations in the accuracy of the underlying data sources and the ambiguity inherent in human relationships.