While electronic surveillance is an excellent tool for law enforcement, they do not serve as an effective deterrent or preventative measure. The number one deterrent is the Human factor.
Vandals and thieves are used to timing down the response time of law enforcement to cameras and alarms, and are skilled getting the most out of the time they have before police can respond to the scene. However, most such criminals do not want to deal with human beings who are in place to prevent their crimes and who can assist in identifying them later to police. Even a small human presence is usually enough to convince would be criminals to seek a softer target to hit.