The overarching, primary use of surveillance is, always and everywhere, extortion. The person coerced is often not the person with a secret, or even the person harmed. "We know your son is doing X. Maybe in exchange for ruling on this case the way we ask, for awarding the contract to the party we suggest, by dropping prosecution of this person we designate, by firing the person we finger, we can let your son slide, this time."

Extortion is the key tradecraft of the FBI: "Testify [falsely] against this person and we will drop prosecution for this crime we have proof you did." Extortion is the key tradecraft of spies: "Get us these documents and we need not notify your daughter-in-law of your son's indiscretions." Extortion made Jeffrey Epstein a billionaire.