I had a reserved parking spot at one time, and someone parked in it one day. I pissed all over the door handle, driver's side window, hood, side of the door, etc. He never parked there again.
I'd say that was a different situation in that it was a reserved spot paid for by me. I wouldn't do this to someone in another setting, even if they are some asshole taking up extra spots in a crowded lot (but I would be pissed).
However, there are certain places where I do park in two spots, but it's never in a crowded parking lot where there are no spaces for others. I go to the back of the parking lot where no one else is parked and take up two spaces so some ass clown doesn't park next to me and ding my car or scratch it.
If I'm in a busy parking lot, I try to always find the end spot and park as close to the end as I can so if some asshole parks over the line or too close, it still gives me some extra room.