[modriano]

Short answer: Cameras produce the evidence needed to build prosecutable cases that can put burglars in jail (thereby preventing them from victimizing/terrorizing people while they're in jail).

Longer answer: People who commit one burglary often commit multiple burglaries. State's Attorneys won't prosecute cases if they don't have strong evidence. The number of burglary victims in a month is basically given by (number of burglars active in a month)(average frequency of burglary in a month). To reduce the number of victims, you could reduce the number of active burglars in an area, and/or you could work to reduce the frequency of burglary by hardening the world, which would be prohibitively expensive. The former strategy is much less expensive, as video evidence is strong evidence, and video cameras have become very affordable and convenient to operate. This helps build stronger cases, which can remove predators from communities, which averts all of the offenses that the predator would have committed had they not been jailed. It is possible to burgle a home with cameras, just as it's possible to get the flu despite a flu shot, but both the cameras and the flu shots help defend more of society against harm.