Back when I was living in Boston, I experienced The Law of the Chair - namely, if you dug out a parking place, you could save that parking place by putting a chair in the place.
I never grasped this. I dug my car out several times, I figured that freeing my car from snow was all the reward I really deserved.
Here's some discussion on this tradition in Chicago: http://www.ericzorn.com/extra/dibs/
What do you think?