There have been studies on teens and their book buying habits. A lot of them. And recent ones have shown both that teens are reluctant to get on the ereader train and that digital sales of YA fiction are skyrocketing. They cite sales of Twilight and Hunger Games and the like. The problem is that those books are selling no matter what format they're in.
Not unlike erotica and erotic romance, a lot of adult women are embarrassed to read YA in public. There is an "I shouldn't read this" attitude that makes reading on digital devices "safer." So, the best sellers are showing an uptick.
A key difference between the erotica/erotic romance digital sales and the YA digital sales is that the YA sales aren't shifting to digital first/digital only publishers. At least not in the same droves. The problem is YA sales are dependent on actual teen readers. They are the ones who give books the push they need to succeed--they're the ones who make a book popular enough that those adult readers hear the buzz.
What that means is those YA digital first/digital only publishers have a daunting task ahead of them. They're trying to sell books to people who don't shop in the same way as their adult readers. Teens don't go hunting for new stores to buy books from. Which means unless the publisher puts a lot of money and effort into promotion, they won't reach that target audience.
What's interesting to note is that there are the occasional self-pubbed YA titles that take off. Whether that's because the author really knows how to target their promotional efforts or they hit with the right book at the right time or they sold their soul... (This is not to say any of those success stories are undeserving, merely to point out that there seems to be a gap in knowledge from those successes to publishers being able to mimic them.)
So, what's the trick? How does one prod teens to go in search of books that aren't hitting the shelves of their local bookstore? Books that aren't the ones all their friends have already read?