&quot; If a law enforcement agency wanted to track someone, it required physically assigning a law enforcement agent to follow that person around. Tracking everybody would be inconceivable, because it would require having as many law enforcement agents as people.&quot;<p>On the other hand, the Stasi and the KGB were infamous for the vast armies they employed in this task. Maybe they couldn&#x27;t track everyone all the time, but they could track enough people enough of the time that people were generally aware there was a non-zero chance of being tracked, and doing anything that might arouse the suspicions of the authorities carried risk. Also, in those societies, everyone was at risk, whereas in the US, the risk is perceived to be weighted toward &#x27;others&#x27;--if you are not in the targeted group, it is easier to be complacent.