I have pirated lots of ebooks where I already own the physical copy. Because I want to both have a paper copy to admire on my bookshelves and lend out, and also I find ereading much more convenient most of the time (I can do other stuff at the same time). But I don't want to pay twice!

I really think paper books should come with a code where you can one-time download an e-version, like you can with CDs now.