This chapter addresses key issues that public policy seeking to support social innovation faces. Combining theoretical insights of the Extended Social Grid Model with empirical results obtained from EU policy surveys and case studies, it identifies key policy implications and recommendations. It first introduces key notions for social innovation policy, including the multifaceted landscape into which support is inserted; the necessity to recognize its political character; to what extent insights from business innovation studies can be useful; and why successful support of social innovation must imply institutional change. The chapter then outlines a series of recurrent policy dilemmas such as whether horizontal support should be preferred; the trade-off between degree and costs of marginalization that wish to be targeted; the difficulty to promote a capability to associate; and how the subsidiarity principle may clash against the need to overcome marginalizing processes.