It's essentially like buying a real book and then giving it to your friends to read it,
Honestly, how many centuries old is the custom of lending a book/lawnmower/whatever to your friend without it being a crime? Do we have to start now?
I mean yeah, it's a very blurry issue with the advent of digital posessions, but if my sister could lend me a novel (which is you know, her property now) without the police crashing the door down, that would be great.
No issue with lending and borrowing (or backups or sharing with your household) personally, it's the fact that it's a digital good and as you said it gets blurry. If someone gives you an old novel there is still just the one novel and borrowing a lawnmower doesn't spawn a second lawnmower so that you and your neighbor can have a lawn mowing race. Anyway that's still not really what bester was talking about. If he and 19 friends each pitch in a quarter and they buy 1 novella and then make 19 copies is that piracy?