The sheer numbers of police on the street is likely the major reason for the street safety enjoyed here in HK as well as that the local populace do not seem at all over charged with testosterone. Also, you don't get them all screaming about their rights like we do in North America.
Rudy Guiliani made his name in New York as Mayor by cleaning up Manhattan with his tough policy on everything from graffiti to broken windows to garbage removal.
What this was based on was the "Broken Windows" idea of renowned public safety commentator James Wilson. The idea is that if you tolerated broken windows, then more would happen. If you eliminated begging, squeegee folks, public urinating, etc, you would have a better foundation on which to build a safer community.
What I have always wondered about Manhattan and how safe it was, was where did these guys all go to. I think they were driven elsewhere leading to others having problems but it did make Manhattan very, very safe.
USA Today has just called Vancouver "the supermodel of North American cities," but many tourists and residents see other major social problems and lots of shootings this year. One person on the net commented that like a supermodel her beauty is skin deep, she's expensive and has a drug problem!
The police are highly trained and for most part do a good job but there simply is no longer enough of them given the drug fueled crimes, gangs and guns. You can shoot a guy on the street there as the police are stretched too thin.
Some of Vancouver and Canada's problems came from lack of services to those with drug problems and the government's theory of putting the mentally ill in the community. It is a great theory but it ain't working as they either turn to crime or they are the victims of drug addicts in the downtown eastside of Vancouver.
Court sentences are lax but the public don't want to pay for more jails,etc and we now have US style justice where one wrong issue leads to a criminal going free. Miranda style - you forget to read them their rights, they walk. It is now like that in Canada.
HK is an isolated cut-off place with strong borders too so that helps.