Why do retirees buy large houses?
Why does milk come in rectangular containers, while soft drinks come in round cans?
Why are gas tanks built into different sides of cars?
Why does Apple charge $150 more for black laptops than for equally-configured white ones?
Why do female models earn so much more than male models?
These may not be the answers, but they are answers...from The Economic Naturalist at Freakonomics.