WhatsApp Neighbourhood Crime Prevention (WNCP) groups are popular in the Netherlands. As a basic assumption, this kind of digital neighbourhood watch could prevent crime, but what is the evidence? Drawing on a mixture of qualitative research and a review of additional publications, we conclude that WNCP groups stimulate social cohesion rather than prevent crime. We reach our conclusion by applying the evaluation EMMIE framework - an acronym for Effect, Mechanisms, Moderators, Implementation and Economics - to the available data. A point for further discussion is the limited scope of the economic dimension. Moral costs must be calculated, too, as WNCP groups tend to deepen divisions between groups of citizens and fuel exclusionary practices in the name of community safety.