^ no idea why this was downvoted. I'm sympathetic to the idea that most real estate boundaries, even though currently enforced by government, are Schelling points that could mostly persist with private enforcement. But that seems like a tall argument for RF frequencies. Sure, if you were right next to the equivalent of an AM/FM station broadcast antenna, you wouldn't want to bother with trying to reuse that frequency. But if you were hundreds of miles away (where its signal is quite low), you could easily reuse the frequency with relatively small power transmitter.
So the current exclusive use of radio frequencies is very much an artifact of government intervention.