Everybody knows San Francisco is the city with glittering streets — well, glittering because of all the puddles of shattered glass from car break-ins. But there’s another pervasive property crime here that doesn’t get as much attention because there’s no evidence left behind. It’s called “porch piracy,” and it’s the swiping of packages off people’s front steps. All that’s left is an empty doorstep and the resident’s frustration.