Some interesting stuff in their fine print:

Prices offered on our site are for items acquired for personal enjoyment use only. “Personal enjoyment use” refers to items acquired with the intent of listening, playing, or watching by an individual. Sorry, prices are not valid for overstocked items, excess business inventory items, items acquired with the intent of resale or items acquired for any other purpose.
Limit of two copies per title per customer. (if you'd like us to make an exception, please email us.) This does not override the Personal Enjoyment policy listed above. We understand that you may occasionally have a duplicate copy. If you have more than one copy of a large number of the items you are selling, we do not consider the items to be of “personal enjoyment use” and you need to contact us before sending the items to us.