Daniel Brendoff sorts boxes before loading them onto trucks for shipping at Amazon.com's fulfillment Center in Fernley, Nevada.

I'm not sure there's a such thing as a pure Amazon.com short.

Remember, only about 2.3 percent of Amazon's float is held short. About 8.5 million shares. Contrast that to Lululemon Athletica, where shorts make up about one-fifth of the float.