@errante Another example is bike locks. Chains can be cut, U-locks can be frozen with canned-air and smashed. If you have an expensive bike it will be a target. But adding 2 locks makes it not usually worth it. Adding 3 locks makes it essentially secure from petty theft, even though a very determined person could still steal it. So is it not worth it to lock your bike? No. Everyone who says "security by obscurity it not security" still locks their bike, because they understand it greatly reduces its chance of being stolen even though it can still be easily broken with enough patience.