I don't have a bike camera, but we do have CCTV at work. One fine day I spotted a person whom I'd previously seen shoplifting in footage from said cameras. As there were no police about, I decided to give him a bollocking myself. He was shocked to say the least, and told me he knew we had cameras but he didn't think they were real. Despite the signs saying they are real. He's never been back, and it would seem he was at least honest in that when he said he'd tell "everyone else" that the cameras were real he perhaps did, as we've had fewer suspicious looking types in since.
However, my point is that the cameras were no deterrent because for one reason or another he didn't think anything would happen - in this case because he thought the cameras were fakes, but I would imagine if it's the case that people think your bike camera is real but they are doing nothing wrong and/or the police will do nothing, it will also have no effect on behaviour.