Their service works a little different from that of Livrada's or the magazine subscription cards I reported on some time back. Rather than just sell cards which entitle the buyer to download a single title, Qinqo also offers author and genre cards.
These other cards were developed with gift-giving in mind. Ever receive a book and wish it were a different title by the same author? That is the kind of problem that the author card is intended to solve, and the genre card works much the same way.
In addition to the cards, Qinqo is working on a vending machine type of concept where the customer can choose a title, buy it, and receive a download code on a slip of paper.
A similar machine showed up in Japan last year, but it is not known whether it has had much commercial success.
On a related note, the Canadian startup Enthrill is having a fair amount of success in signing up retailers (including booksellers) in both the US and Canada. They're not quite ready to go public yet, but when they are you will be surprised.