Would you buy a used MP3?
A company called ReDigi tried to open a used MP3 business, presumably where you could find copies of Lou Bega's folder of mp3s for under a dollar, and maybe buy a t-shirt with a pot leaf on it.
Kidding of course—ReDigi was a website with a "media manager" that you could download. The "media manager" enabled you to access a marketplace, where you could purchase "used" digital files from other users, and sell your own. It was designed, supposedly, so that once you'd sold a song, you wouldn't be able to hold onto it any longer.
A Judge found this situation a little suspect:
ReDigi’s service, he wrote, “infringes Capitol’s exclusive right of reproduction” as well as its “exclusive right of distribution.” And Judge Sullivan went further, concluding that “the Court cannot of its own accord condone the wholesale application of the first sale defense to the digital sphere, particularly when Congress itself has declined to take that step.”
Resale of CDs, though, is alright; owners of CDs can resell them without getting the OK of the copyright holder.
If this seems strange and contradictory...well, that's the nature of selling digital music in the MP3 era.
Read about the specifics of the case here.