are more cameras the answer?

In reference specifically to the Boston incident, cameras did not deter the bombers. They seem, in fact, to have had an utter disregard for them.

In general, I honestly don't know. It's worth a shot, however, since there is not one quantifiable objection.

There will be the reduction of crime with increased surveillance, but it is what the crimes are that bother people. if you shoot someone and there's cctv, you'll get put in prison. if you just say a couple of words, and you are jailed (because the cameras heard you) that is an altogether different story. Don't worry yourself.