Heck, at least half the people on HN won't get why coal was chosen. Perhaps an answer as to "Why coal?" would be appropriate on the home page.
Also, there is no call to action (or it's not clear enough). I clicked through to the cart and it gives me a three-step explanation but no links or buttons that say "Click me to get started". I was on the cart page and, at the bottom, it just says "It appears that your cart is currently empty!" This could be massively improved if you just sit your mom (or someone non technical) down at a computer and watch what they click while trying to accomplish a given tasks (or just exploring).
The reference to "The Naughty List" makes it clear why coal was chosen: Santa Claus has been believed to make a list of children throughout the world, categorizing them according to their behavior ("naughty" or "nice") and to deliver presents, including toys, and candy to all of the well-behaved children in the world, and sometimes coal to the naughty children, on the single night of Christmas Eve. [1]
My first thought was obviously that of Santa Claus, and leaving coal in the stockings of naughty children. However the commentary here and the text on the website lead me to think it was perhaps referring to something more localised to America or its politics.
FWIW packages sent to member offices get scanned by a mail processing center off site, I'm not sure if they'd actually deliver the coal on to the office or not =P.
The dust of coal itself can also have adverse health affects if inhaled. You might want to properly shrink wrap the coal. You don't want some poor unpaid intern to get a whiff of coal in their lungs between when they open the package and throw it in the trash. The workers who inspect all packages might not appreciate it as well.
Also, there is no call to action (or it's not clear enough). I clicked through to the cart and it gives me a three-step explanation but no links or buttons that say "Click me to get started". I was on the cart page and, at the bottom, it just says "It appears that your cart is currently empty!" This could be massively improved if you just sit your mom (or someone non technical) down at a computer and watch what they click while trying to accomplish a given tasks (or just exploring).