[babygene]

" If you send electronic copies, it would be very hard to prevent copying"

Nothing keeps you from copying a book printed on paper either.

Though it may not be cost effective to copy a novel, much of what people check out of libraries is technical works where all you might need to copy is a table, an article, a couple of pages or a chapter.

[HairOfTheDog]

Ease, expense and quality of the copy prevents widespread copying of books. The distribution is limited and not a concern. It is not nearly in the same league as instant worldwide access of free copies of works that are indistinguishable in quality from the original.