The problem Chorder solves

You never own the content that you buy from Kindle Store/iTunes etc, even though you have paid the full price for it. It just sits in your (digital) shelf ideally for eternity, once you've consumed the content. This is not the case with physical books, or CD/DVDs. You buy those, you own those. You get to do whatever you wanna do with it. That's because DVDs and Paperbacks belong to the realm of atoms, while digital copies are in the realm of bits. It's the digital abundance that's the issue. You bring in scarcity to the digital realm, you can make digital content behave more or less like their physical counterparts. In that scenario, a content owner is the true owner of that particular copy of the content. They become collectebles and a whole new market is created out of it.

Challenges we ran into

Bugs all around. It was a pretty complicated system to begin with already.