Fashions change every season and when we buy new things we have to get rid of the old, outgrown and out of style. Americans consume 65 pounds of new clothes per person each year and discard a total of 25.4 billion pounds of textiles annually.
Tell the flight attendants you want just the can, no napkin, next time you need a shot of carbonated caffeine while in the air. Why use so many plastic cups, and what happens to them when the plane lands?
Understanding the "life-cycle" of any consumable good offers a fairly accurate sense of how "green" it really is -- basically, where things come from and what happens to them when we are done with them.