IB  Ingrid Bergman in the 1944 film “Gaslight”

“…the Stasi often used a method which was really diabolic. It was called Zersetzung (gaslighting). The word is difficult to translate because it literally means “decomposition.”  But actually, it’s a quite accurate description. The goal was to secretly destroy the self-confidence of people, for example by damaging their reputation, by organizing failures in their work, and by destroying their personal relationships. Considering this, East Germany was a very modern dictatorship. The Stasi didn’t try to arrest every dissident. It preferred to paralyze them, and it could do so because it had access to so much personal information and to so many institutions.”
—Hubertus Knabe, German historian

One of the problems with en masse surveillance is that gives a government the power to psychologically attack anyone whom they do not like.  This has happened before, and it is happening now in some places. The STASI perfected gaslighting, and this perfection was based on their eavesdropping against the population.