I don't really have to watch out for thieves. Of course they exist and you can never be too careful with these things. But occasionally having left valuables in view inside my car, or a bag at a cafe table while I visit the restroom, I've never had anything stolen. I'm not afraid to walk in the city at night.
A friend of mine was robbed at gunpoint in broad daylight in SF, which came to me as a big surprise. I couldn't imagine that could even happen. Obviously I need to travel more to broaden my worldview...