Damn man, this is the biggest worry I have. Coming from a 17 year old Mustang (that used to get vandalized all the time about 10 years ago when I first got it), one thing I no longer had to worry about was people thinking my car was "too night" and deciding to key it, scratch it up or break into it.
I DO have an alarm system, but I am in areas that aren't always the best. I'm actually moving into a condo across the street to lease the garage they offer. But I'm still worried somebody will eventually key my car for no reason when I'm in a parking lot somewhere.
I'm thinking that because my car is Titanium Silver, it's not a color that pops out as "too shiny...must key!"