Tim, why are you so opposed to invisible policing in a public area? Its a totally different ball game to them monitoring your private actions like email.
Also, invisible policing helps catch people who think they can get away with it. And those kinds of people wont stop breaking the law unless visible policing is everywhere all the time. Now tell me, which one is the more practical and feasible solution in a country with a lowish population density? Nevermind that visible policing is quite easy to work around - "oh look, the car just drove past, so we've got at least 20min to do xyz"