I'm usually the first to defend the police but I have to say my experience was not this positive - with regard to the stalking case i mentioned originally (the one where the stalker was photographing my then girlfreind, photoshoping her face onto porn and posting them arround her work place, and distributing "call for hot sex talk" cards with her number on arround phone boxes in unsalubrious areas) the police actually did very little - they spoke to him and he basically denied doing it and they couldnt do anything else, it wasnt their fault , just one of those things that come from their hands being tied.
In this case I eventually braced him and after i got his attention I explained robustly that i found his behavior unacceptable and that he jolly well better stop it or i'd be very very cross (this isnt an exact description of what went down i recall there being rather more words that I can't use here) and the stalking stopped imediately.
This is only tangentilally related to the OP , but the point is (apart from my point above about extreme situations requiring extreme measures) that just because most people with a camera are doing nothing wrong it doesnt automatically follow that absolutely everyone is.