Just imagine casino A would pay some guys to carry advertising sign inside of casino B. Those guys would be removed instantly.
Or let's say somebody creates a AR game where you can leave signs with random texts everywhere. And then somebody decides to plant a sign with "OP is bundle of sticks" on your property. In the real world you can just remove the sign and call the cops, but what would you do in the AR world?
If there will be too much shenanigans I can see that in the future your real property boundary might translate into the virtual AR world.