Just a thought...
With the mass spread of apocalyptic thievery, I have basically given up building anything and just working on building character level. But what about the following to divert this issue:
Fences and Dogs. Dogs can be found in the wild and when caught, they can be trained. The more training, the more ferocious. However, since people still have friends that might not be part of their group at a given time, dogs can be trained not to attack friends or unknown persons unless the owner sets his dog to do so/is offline. Fences can also have a degree of difficulty to get over. A simple picket fence is annoying to get over but a 7 foot barbed wire fence is something else.
If it's necessary for peeps to thieve, fine. But there should be levels of thieving ability which maxes out at ninja awesome.
Locks have been mentioned. But what about different degrees of locks?
And Traps. If it were me in real life, I'd Trap my goods. That or Hide them. Bury underground so that it'd be difficult to find unless someone brought in a Dog or Dowsing wand.