Recent years have seen a growth in the use of social norm messages by local and national governments. These messages have been primarily used to induce desired behaviours among the non-compliant minority by pointing to the compliance of the majority. As well as being of considerable theoretical interest, these messages have an unusually high level of empirical and experimental support in government settings. In this paper, we review many of these applied experiments in a bid to understand the workings of social norm messages and, just as importantly, where they do not work as well. We also discuss why this kind of intervention has attracted such an unusually large body of experimental evidence.