"There was a story earlier about Florissant having a law against this same thing!"
I think the neighborhood should dictate your habits on this. If I lived in Northwoods, no way would I leave my car unattended and running ( locked or not ).
Certain areas of Florissant I would be leary of as well.
This happens every year when it gets cold. You would think people would learn.
One way to prevent this is to just install "The Club " on your steering wheel while you warm up your car. Thieves won`t mess around to long in daylight in front of your house to try and take a car. The devises also make good weapons you can legally keep on your floorboard. : )
I leave mine running to warm up all the time. But I leave for work at 0245, theres not many people out at that hour. On the other hand, I live in the neighborhood in Florissant that hosted the "Garage Sale" shooting last spring, so I probably shouldnt do it at anytime..