If you have a CD or book you don't want anymore, you can sell it. The law says that's perfectly legal. But what about an MP3 or an e-book? Can you legally resell your digital goods?
This was the question before a judge in the case of Capitol Records v. ReDigi Inc.
Launched in 2011, ReDigi is basically a digital version of a used-record store. You can sell the company your old MP3s, and you can buy "used" MP3s that other people have sold.