No, I never break the spine. I do sometimes open the book from both sides and then go towards the middle from both sides, so that the spine doesn't break but the book is easier to open. But I hate it when people do it to my books! I had a school book with me once to class, and my classmate asked if she could look something up. She took the book, opened it in the middle, and opened it WIDE. She made a line down the spine... I felt like screaming! And I always try to keep my books nice and clean...
Btw, why do some people write in library books? I once found a shopping list written in the margins... And people marking with marker pens and normals pens, underlining, folding pages, etc.
