I've completely given up on parking at the back of the lot to avoid the idiots, as when I do, the problem is actually worse!
Even in -30deg, I always seem to end up with a vehicle on each side on me, and you'd think they would at least leave enough room to open the door.
Now I try to find a spot with a curb on one side, and park with the drivers door to the curb so at least i can into my truck.
I also give out 'tickets'. I print the following on heavy yellow paper, sized to mimic a real parking ticket.