Some of the disadvantages of CCTV cameras include a false sense of total security, the inability to stop crimes that are in progress and the inability to use recorded footage as evidence in police investigations. It's best that CCTV cameras are used in conjunction with an alarm system in order for them to maximize their effectiveness.
CCTV cameras can lull home and business owners into a false sense of complacency. While criminals might hesitate when they spot a CCTV camera, they too realize that cameras have their limits when they aren't paired with environmental hazard detectors, electronic access control panels and alarms.
CCTV cameras can record a robbery or crime in progress, but they can't do anything to actually stop the crime. It's important to use cameras in conjunction with alarm systems so the proper authorities can be alerted of the crime as it's being recorded on the camera. Cameras by themselves can't prevent victims from having to fill out police reports, filing insurance claims and having to replace their stolen or destroyed belongings.
If criminals are wearing masks or have their faces obscured while being recorded on CCTV cameras, there may be very little that the police can do to successfully identify them if there isn't more useful information to use.