Advertising on E-Book Programs

I've have a Droid for close to a year now and I love it.  Knowing I would be in the car during spring break as our family road tripped I decided to download a bunch of different games to play.  It was great, mostly for my wife because I did most of the driving but none the less it was easy to pass the time playing mind puzzle games.  Most of the games I downloaded were free but come with the stings of having advertising on them in some form or another.  So the e-book idea works very similar.  Instead of paying $9.00 for a book you can only read on your kindal/iPad/whatever you get the book for free or for a reduced price of $1.00 and then it comes with advertising.  For a company looking to hit a niche it would be a gold mine.  Want to target teenage girls who love to spend money on posters of hot movie stars?  Spend your money with the next Twilight book.   This is very closely related to the advertising insert in a hard bound new release blog I did a few months ago.