zlacker

It very clearly is. By watching ADSB data, I can build a picture of your travel patterns. I will be able to determine where you go, when, and could lay an ambush for you once I've found a pattern.

Same thing if I put a tracking device on your personal conveyance.

AF1 routinely turns off their ADSB transponder, as do military aircraft. They generally do not when operating in high traffic areas, but will if they are over commercial airspace and want to mask their position.

While this data's purpose is primarily for safety and to make ATC job easier, it was never intended to used as a public tracking system.