It's not just street crime, either. The first building I lived in had its bike lockers broken into by a pro crew in masks, and tens of thousands of dollars of bikes stolen. I also forgot to mention the man screaming at the top of his lungs at a woman waiting for a bus, the coworker who fought off an attempted mugging, coming back to my car (probably at Lands End) to find one of the screws missing from the license plate, and other stuff I only heard about rather than saw.

Based on this thread, there's a lot going on that people are lucky enough not to notice, or choose not to notice, but it definitely makes SF a risky choice for businesses. I probably fared as well as I did because I'm tall and didn't go out much without other people with me.