How is positive-sum privacy feasible?

This work discusses Ann Cavoukian's fourth Privacy by Design (PbD) principle, which is known as Full Functionality Positive-Sum, not Zero-Sum. The authors argue that this principle regulating trade-offs between privacy and functionality is questionable from a theoretic as well as from an operational point of view. A more consistent and pragmatic definition of positive-sum privacy is proposed and demonstrated using an example scenario in the context of video surveillance.