There are a lot of things that I use to varying degrees depending on the risk and the setup. I have had bear and elk destroy my cameras, but they have never been stolen by people.
Hiding the camera is the best defense. I have filmed people sitting within 5 yards of cameras for hours at a time and never give an indication that they noticed that they were on camera. I have also had three different occasions where I told landowners exactly where a camera was, then got photos of them looking for the camera, and later they told me that they couldn't find them.
The python cable lock is awesome. I use them on cameras quite often. I also use them on bear bait barrels. In addition to the security, it helps get the camera snug against the tree much better than chain or other cables.
If I am packing in I save weight by using screws instead of cable. I use less common heads so that some guy with a leatherman in his pocket won't be able to take it. Some cameras are made to accept screws and some would need a case or modification. I did have one of these cameras get noticed by a hunter, but he either wasn't inclined to steal it or couldn't get it off.
I do also often have multiple cameras set up in an area, but that is more about catching all of the wildlife activity as it is about catching a thief. I have detected several trespasses and illegal off-roading on my trail cameras, but just having someone's photo doesn't do any good unless you know the guy or have some way to figure out who he is.
Legal issues: There are some general exemptions on federal land for legal hunting activities. They allow us to bait bears, put up tree stands, and build blinds without getting charged with littering or building structures. These exemptions are broad enough that I don't see why they wouldn't allow a trail camera to be screwed to a tree. A forest or BLM district could have its own exemption, but as far as I know these rules are good for almost anywhere it is legal to hunt in the west.
Public land also has a first-come-first-served policy for blinds and tree stands that are left by other hunters. The same policy is not specific to blinds and tree stands, and has been accepted to apply to shooting over someone else's bait as well. It is illegal to tamper or remove someone else's blind or stand, but it is perfectly legal to sit in it if you beat them to it on any given day. I would think that the same policy would apply to getting photos off of someone else's camera on public land. It is probably illegal to delete photos or turn the camera off, but as long as you leave it how you found it, I think that public access laws would have you covered. That said, I wouldn't feel good about downloading someone else's photos, just like I don't feel good about beating them to their own blind. If anyone ever has downloaded my photos, they will probably think that nothing has been coming in for the past week (because I set it with last week's date).
, deleted the photos of just myself and "put it back where I found it" and made sure it was still running correctly.
