When I lived in my old apartment complex, I would marvel at one woman who would walk down three flights of stairs to start her car and would leave it running for a good 15 minutes or so. Really? It's just unnecessary people. While researching this subject, I came across this interesting bit of information. "Idling for long periods in cold weather can actually cause excessive engine wear," the EPA notes in a report. So, this practice is both bad for your car AND bad for the environment. And it wastes gas.
*If you are reading this and live in an extremely cold area of the world, then do what you want. For the Southerners out there who can't stomach the cold weather, TOO BAD! Be kind to Mother Earth and to your car and stop idling.