Different kinds of Crime Prevention (CP) activities are functions of most governments, but, which such activities and why? Security services can be provided by private firms. Thus, we ask, when does the private market work, and when does it not? That is, what key characteristic(s) cause market failure for a club good, a commons good, or a public good? What are examples of particular CP activities that have one or more of those characteristics? For those CP activities, why would the private market fail to provide the optimal amount of security? What can government do to raise social welfare? Which CP activities are best conducted at the local, state, or national level?