I'm not saying this because I support the idea of people breaking into stores and whatnot, but I think it is because someone is sitting behind that computer screen, watching your evry move. Even in schools! A stalker could be there, a pervet, a pedophile. But I think they should be used sparingly like (for instance) in stores for robberies.
Of course, security cameras COULD be used to track your actions and whatnot. I don't doubt it's possible that the NSA gets live cam feed wherever they want to. However, it's not invasion of privacy if the cameras record you only when you are in public. We should get worried when it's mandatory for everyone to have security cameras inside their own houses.
Security camera not only stop crime but also can save your life. The installation of security camera can help to deter wrongdoer to commit a crime. According to some credible evidence, surveillance camera can reduce murderer case effectively .Without a doubt, It is a idea protection for your property and life.
People place security cameras in places that they could see anyway. If it is in someone home or business, obviously the owner of the home or business should be able to view those places. Anyone else entering that home or business would know that the place is not theirs so would not be private to them. In cases of security cameras in public places such as roads, and such, these are PUBLIC places were there is not expectation of privacy. If there is no expectation of privacy, how a camera be an invasion of privacy?