The Empty Box

It's possible that warehouses occasionally send out empty boxes by mistake, or due to negligence or theft. Possibly not as many as customers claim, but it's possible. Here are some theories about why it happens:
 * The customer opened the container, then the dress magically dematerialized after they wore it to the prom and spilled tapioca pudding all over it, never to be seen again.
 * MP3 Players come with built in legs that cause them to walk to the houses of warehouse employees.
 * The warehouse deadline is so tight that boxes are slapped with shipping labels and sealed before the product enters the container. Nobody notices that it weighs under 1 ounce.
 * The customer just wants another Nintendo DS.
 * The clothing elves went on strike.
 * The label on the box said "Caution: Expensive Jewelry Inside.  Handle With Care" and it proved to be too much temptation for the delivery truck driver.
 * Postal workers have access to X-Ray technology.
 * There are street gangs that just sit on the corner and wait for the delivery truck to leave things on people's porches, and they have tape guns.

This may also happen with returns when:
 * The customer writes: "Please refund me for this $200 dress" on the box.
 * A ninja hides on the customer's ceiling, swiping the item from the box with a grappling hook while the customer is getting their tape gun. The customer never notices that the box is strangely light.