This is a repeat article of a business borne in Japan fueled by iPads and lack in home shelf-space in big cities. http://www.wired.com/gadgetlab/2011/02/japanese-book-scannin...

I think they scan new books, once they have one scan in inventory, they don't have to scan it again. When you send them your book, it's proof you owned one and they send you a PDF. That is, they don't scan all individual books --so if yours had margin notes, that would be lost, I believe.