I happened to be browsing CNN and noticed a story entitled, "Cameras that scold." The short description read:
"Residents and police say talking surveillance cameras reduce crime. CNN's Gary Nurenberg reports ( April 8 )"
Basically, the city of Baltimore has, at residents' requests, installed surveillance cameras that are activated by motion detection sensors. Upon activation, it alerts:
"Your photograph was just taken. We will use it prosecute you."
You can check out the video here. (Just to warn you in advance, it's a pop-up window, so you may have to adjust your pop-up blocker.)
The assumption, by the community - both residential and law enforcement - is that crime has been reduced since the implementation of these cameras. However, that's not what one can really conclude. The cameras are isolated security measures; that is, while they may deter criminals from the target they monitor, this says nothing about reducing the amount of crime that will actually take place.
What you have here isn't a way to solve the problem; it just moves the problem somewhere else. You see this a lot - protecting targets (especially those already hit). This isn't practical, nor does it make sense. Have you tried counting all the possible targets? Me neither. Suppose we have a front door and back door. A criminal comes in the front door, so afterwards, we install surveillance cameras above the front door. Does this reduce any crime? No, it just lets the criminal know that he'll have to use the back door next time.
There have been numerous reports on the ineffectiveness of surveillance cameras; it was also found more effective to just increase lighting in areas prone to crime, and have more law enforcement units patrolling such areas. The important generalization here is to make sure that your security measure doesn't relocate the problem; it should reduce the occurrence of it. As taxpayers and consumers, this affects us.
Even in a computer security context, it's important to make sure your security mechanisms are cost-effective, and not just a deterrence that point adversaries to another target in which to mount their attack. Again, this is another situation where those with an influence on decisions, and those who ultimately make them, don't understand the concept of making good trade-offs. The cost is real, but the security isn't.