My niece (14) has a Nook that my mother bought her, my mom has bought her e-books, and for last Christmas I got her a prepaid card for the Nook store, so she can buy some books herself.
I think that's a common practice, as few parents are going to purchase books for their teenagers, and their teen kids aren't about to tell their parents what they're reading.
We can never figure out what to get my nephew (23), so everyone gives him bookstore/app store gift cards, so it's not limited to juvenile readers either. That said, Kindle is better than lulu, smashwords or D2D, because no one gives those as gifts.
Also, don't assume that you can't include erotica in YA novels, but it's got to be a gradual buildup, focused on the relationship, rather than having two people jump into bed as a way of getting to know each other (i.e. write it for women, rather than horny males). Young kids also prefer dystopian YA novels, because they assume everything adults do is fucked up, and it's up to youngsters to set everything right (sound familiar, anyone?).
Note: These are all observations based on my never having written a YA story.