This decision is in no way surprising to anyone who knows copyright law. US Copyright law *explicitly* states that you do not have a right to resell digital copies, and if those guys had a lawyer advising them on their business when they set it up, they should be suing him for malpractice now. Look up "First Sale Doctrine" if you're having trouble sleeping.
If you're a cynic (as I am) this is evidence of the ridiculous influence of copyright owners on Washington.
However, there is *some* rational for this - if you buy a CD and then sell it to someone else, no new copies have been made. But, if you buy an MP3, and then sell it to someone else, to do so, you must make a copy. Which means you're now in copyright territory, since you're selling a copy of the work without the author's permission.
Now, personally speaking, I think if you're going to certify your copy has been destroyed, this shouldn't be a problem - but that's the law, now, and has been for more than a decade (maybe longer, I started paying attention when I was at EMusic ca. 1998).