My old roommate Mark had an ancient, broken-down Chevy Mustang that darkened our garage for more than a year. When it came time to move out, the car had to go, but Mark was out of town. So my friend Eric pushed it onto the curb and stuck a For Sale sign in the window advertising a 'Sweet Pony' at a low price. He put my roommate Graham's phone number on the sign but never bothered telling him. It sold, but not to the guy who called and offered Graham the highest price. Mark ended up giving the car away for free. His choice would have been baffling if it weren't for the wisdom Graham had offered years earlier: "The only motivating forces in this house are spite and irony."