And, of course, there's a bunch of licensed FM stations who are anxious to turn in any pirates who might compete with them, and they aren't above lying about 'interference'. (On shortwave, on the other hand, you pretty much have to piss off the wrong guy, right "Commander Bunny"?)
Hell, licensed stations routinely file objections with the FCC, to any new station attempting to become licensed in their market area. It's their "standard operating procedure". Some of those even have the balls to tell the truth about their motivation: "If you license this new station, it will hurt our revenues." I guess 'socialism' is fine as long as it's the established capitalists who are benefiting from it; competition is something with which they should not have to be bothered.
Yes, it's easy for the FCC to track you down on FM (or any other frequency range) if they actually bring a vehicle to your town, or just happen to be there doing routine monitoring of licensed stations when you go on the air. But if you're not within line-of-sight range of any of their monitoring facilities, they aren't going to know about you until someone complains. If you don't go 24/7 or many days in a row, but instead do a more "hit and run" operation which does not repeat for, say, a month or two, you could get away with it for years, or even forever..