Well for starters... 1/4" plate steel with spikes is overkill.
so yeah, besides- the cost involved in doing something like that would probably pay for a lot of dent removal.
Chances are i wont do anything except be more mindful of where i park - but sometimes you dont have a lot of choice - and other times you can't predict whether or not someone will park next to you while you are away.
i just think it is ridiculous how some folks out there have no respect for the property of others.