> I think the concern is irrational; the alternative (having agents manually tail people) is error prone, > subjective, incredibly expensive, and no less intrus

> I think the concern is irrational; the alternative (having agents manually tail people) is error prone, > subjective, incredibly expensive, and no less intrusive. Don't underestimate the role of the "incredibly expensive" part. The physical and resource constraints for tailing people limit law enforcement's ability to do that. In this way GPS trackers are more intrusive than traditional surveillance methods, in the sense that they can be deployed indiscriminately at a much larger scale. (For a related example, in "Code" Lessig argues that the US founders didn't need an explicit right to privacy since it was implied by the search-and-seizure and trespass constraints. Prior to electronic surveillance methods, it was difficult to invade one's privacy without already violating trespass or similar laws.)