From TechNewsWorld: Neighborhood Watch 2.0:

City budgets are straining police forces in many cities, and in some cases citizens have seized upon social networking technologies to help guard against crime in their own neighborhoods. It’s unclear whether neighborhood watch efforts actually make people safer, but statistics indicate that neighborhoods with high levels of resident cohesion typically have less crime.

This is another example of how better communication (or cohesion) in a neighborhood can help make it safer.