In this article we discuss the nature and productivity of informal innovation networks, i.e. informal collaborative arrangements between organizations engaged in product or process innovation. Such networks can be used in any phase of the innovation process, but their informal nature makes them especially suited for its fuzzy front end. We explore their potential in technology exchange and learning on the basis of a combination of organization network theory and knowledge management theory. We discuss issues in network governance and network operational management and discuss the basic dilemma – which we named the Daphne-dilemma – facing attempts to improve the productivity of informal innovation networks: too little management effort may lead to under-exploitation of their potential and poor productivity, but too much management effort may destroy their informal nature and hence their creative and explorative potential.