Hey, how do we know the bestsellers list (on websites) are really bestsellers? The list could mostly consist of bestsellers with a few popular titles that they really want to push out of their inventory. Putting it in the bestsellers will make people think it's more popular than it is, which might persuade them to buy it.

"Tons of people thought this DVD was worth buying. Hmmm, maybe it is. Okay. [click add to cart]"

Damn, those guys are sneaky.