Behavioral economics at Starbucks: should paper cup users be penalized?

Starbucks generates 4 billion paper cups a year, or 12 cups for every man, woman and child in America. The coffee giant knocks ten cents off beverage price for customers who bring in their own mugs, but Mark Gunther writes: "If Starbucks really wanted to save trees, it wouldn't offer discounts to people who bring mugs. It would charge a dime to everyone who does not."