Just carry a concealed firearm or go with someone that does. I always go out with a concealed Glock Model #27 .40 (installed with Laser-Max Laser). I had some nut follow my wife and I to our vehicle around X-Mas '07, he told me to give him my bags or he was going to "make me bleed", I turned around and he had a red laser-dot illuminating his head. He said he was "joking" and thought I was his "friend" (OK!), he turned and ran back through the parking lot. In this day and age with the economy and people quite desperate you can't take chances.
Well done. My Springfield XD in .45 gets the point across quite well too.