Videotaping, interactive websites, cell phones, and desktop publishing are all tools used by the “electronic posse,” a term coined by the journal Governing to describe people who are willing to do something about the crime in their neighborhoods. Residents in a town in Massachusetts, for example, videotaped the prostitutes and drug dealers who were taking over their neighborhood; within six weeks, the criminals had fled.

Citizens in the electronic posse usually work in conjunction with police through community policing programs. Community policing aims to prevent crime before it happens by encouraging law enforcement officers to help residents patrol their own neighborhoods. William D. Eggers and John O’Leary, authors of a book about community policing, argue that “restoring public safety demands a renewed partnership between the police and the community.” Advocates maintain that in addition...