"I'm thinking about buying a more fuel efficient car." "Why?" "It's my patriotic duty to reduce this country's dependency on foreign sources of oil." "Why?" "Because then the countries that hate us will have less money to fund terrorists." "Actually, developing countries would buy the oil you saved, thus adequately funding those same terrorists." "At least I wouldn't be funding them myself." "Oil is a fungible commodity. The capitalist system virtually guarantees that you'll end up buying the lowest cost oil from sources unknown to you." "Well, maybe, but I want my car to make a statement." "And the statement would be 'Hey, everyone, I don't understand what fungible means!'"