As much as they like the idea of selling single titles, DC knows that the real money is in recurring subscriptions. That's why they're looking to use the subscription features available for iBooks, Kindle, and Nook. Hank: “We don’t currently offer subscription options but are considering this as a possible future digital feature. Stay tuned!”
Hank also indicated that DC is working to add their back list to all the ebookstores. “We will be adding backlist titles over the next few months, more will be added each week, in addition to the same-day digital and digital-first titles that are released weekly.”
But one thing which DC Comics won't be able to do is offer cross-platform availability. Comics bought in one ebookstore cannot be transferred via an external account with DC Comics. Of course, this silo issue is shared by all publishers, so DC is not alone in having their hands tied.