I mostly walk, sometimes I take public transportation and more rarely use my families car. I get really mad when people park their cars across the sidewalk. It's an annoyance for me, but when I see a disabled, elderly or young person leaveing the sidewalk to navigate around someone who has decided to make that portion of their driveway which is a sidewalk their parking spot I get enraged. There is a giant halfway house one block away from my home for people who are either disabled or recovering from phisical or emotional trauma. I have watched them navigate these hazards many times.
I have protested this kind of parking in a variety of ways, ponder it and you will probably think of a few of them. The problem with these types of protests was that it wasn't changing anyone's behavior.
I was dissatisfied, I wanted people to pay enough of a price that they might either learn a lesson or have to pay a price that made blocking sidewalks undesirable. Someone close to me has access to a high quality printing press that was occasionally used for art, hijinks, or whatever fun project we could think of. I asked her to make me these stickers.
I put them on the front windshield, driver-side. It is rare to see the same car blocking the same drive more then once. I have given a few stickers to other walkers some of whom have come back for more. I think it was a good, non destructive solution to this sort of antisocial behavior, I think it's a solution that suggest's I might have learned from my education in economics (incentives/disincentives) and my gradual maturation from a person who readily engaged in dangerous confrontations to someone who can seek out lower risk higher reward solutions.