There are some jealous ppl out there, I am sorry and do share your pain. I park as far away from others in any parking lot or try to park next to similar types of cars, e.g. MB, Porsches, etc (hoping they don't leave anytime soon).
Funny story two nights ago I went to the mall, I parked at the end of the row no cars around for a few good spaces in between. I came back out to find parked right next to my car (on both sides) were two 3 series. It looked like a group meet..It was nice to see I wasn't the only paranoid one out there.
'07 Audi A8 (w/ 20,000 miles)
'03 745Li (sold)
'03 Acura TL-S
'02 Infiniti QX4 (sold & new owner totaled it 4 hours later)