I guess it depends what you're doing. Remapping some engine timings, where the worst thing that could happen is you blow up your engine: mostly fine, although

I guess it depends what you're doing. Remapping some engine timings, where the worst thing that could happen is you blow up your engine: mostly fine, although there's a small risk that you cause an accident if that causes you to lose acceleration on the highway. Reading OBD or CAN buses, fine. Writing to the buses: nope nope nope. And that's just for cars. Flying cars, where many system failures result in an inability of the car to stay in the air: I'd expect this to be thoroughly illegal and heavily prosecuted, because I for one quite like being alive and not underneath a crashed flying car. Does this stifle innovation? For sure. Does it restrict one's ability to modify the things you own? Definitely. Are aircraft regs sometimes over the top? (For instance, preventing you from updating old built-in gps systems, as came up on HN recently.) Yup. But the regs exist for good reasons.