deterrents are simply about not appearing soft, while a camera's presence does imply some sort of hardness.. a lack of a camera does not imply any kind of softness, infact a lack of a camera can imply hardness too.. take for example, you can tell an employee (sitter, serviceman) that you have hidden cameras around and it's effective weather or not you actually do or not.. because they will presume they are being watched.. if they can see the cameras and think they know all there FOV's they can determine blindspots, and they will.
Lots of cameras can actually imply an incentive, it means you have something of great value to protect.. if your in the ghetto and have a dozen visible cameras you might just get your door kicked in and a few gangbangers demanding you give them money or drugs simply for the cameras alone..
Thieves know how to spot cameras if they want or they been busted by them before.. hell you do and your just an enthusiast, tell me you havent spotted every camera in your neighborhood already? I cant go anywhere without spotting an antenna array, security camera, fiberoptic interconnect.. they just jump out at me because I find communications and security infrastructure interesting.. Just this weekend I was scoping out the cameras at a kids birthday party in a local park and traced it to a Ubiquiti Point to Point access point.. that was directed at the municipal building next door where I could see another Ubiquiti on the roof.. If I wanted to blind all those cameras I knew exactly what would need to be done, and im not a criminal anymore since they legalized it.
Consider if they spot the camera they often looked into the camera directly and gave you the best chance at a facial shot your going to get.
Take a balanced approach, make them discrete enough you dont look like a paranoid freak sitting on a mountain of gold/weapons/drugs.. but visible enough that anyone looking for em will have no trouble locating them, and then put a few in that nobody but you know about.. but never rely on obscurity for security; its a fallacy that traps many so called security experts and amateurs.