Surveillance cameras probably do need to be in certain public spaces where crime might happen and in police search situations, but they need to be used sparingly. And anything that can be abused by government and police probably will be so the odds are that our privacy is being invaded.
I believe that there is a fine line between the need for security and the right to privacy. I believe that our government has crossed it. Not only do they place an increasing number of cameras in public places (even when no criminal act has taken place there), they look for key words in emails and phone calls that might be signs of terrorism. They also look for patterns in transaction of all sorts and decide whether to investigate someone (i.E. Use GPS trackers on them, read their phone calls, place cameras in their cars, etc.). Is this an invasion of privacy? I say yes.
Surveillance cameras do not constitute an unreasonable invasion of out privacy and are not likely to result in abuse by the government and police. The cameras are not in your home or and other private place. They are in public areas, and the cameras there are meant to help protect you.
I believe security cameras have been put in place for very good reasons, so I do not believe they are an invasion of privacy. A person shouldn't expect an abundant amount of privacy when they are out in public. Since security cameras a privy to areas where anyone else could see or hear you, I don't think they are a harm. However, since they are there I am sure the government or police could abuse them and I would say that is fairly likely.
Only criminals care about surveillance cameras. They can only see the public areas around a place and the private areas inside the place that decided to put them up. This is in no way an invasion of privacy. No public places are private. This means that their is no invasion of privacy.
Unless security cameras are aimed directly at a person's home, they normally don't present an unreasonable invasion of privacy. Government and police can abuse these cameras, but surveillance cameras on their own don't necessarily constitute abuse. These agencies should be able to use these cameras in limited circumstances for public safety.
Surveillance cameras are there for our safety. They are not an invasion of privacy and are not abused by the government and the police. Without surveillance cameras, we would not be able to catch the amount of criminals that we have caught and we would not be as safe as we are today.
When we are out in the public, it is safe to assume that at all times, we may be being observed or even filmed. This is done for our own protection, even though it may feel a bit unnerving to know we're being watched. As recently as the Boston Marathon bombing, we can see how cameras worked to apprehend criminals and protect society from further harm. While we have a tradeoff that's not altogether pleasant in order to be more safe, we need to remember that cameras are being used by law enforcement and the government to keep us as safe as they can.