To lend books or not may not have the gravity of Hamlet's question of simply being, but I will admit that I feel such contradictory impulses. First, I know that I have a genuine need to talk about books I read with others who have actually read too. I know that sharing one of my books doesn't guarantee that will happen. (In fact, I know because of the number of borrowed books sitting unheeded on my shelves. They ooze guilt.)
Only through trial and error do I learn who returns books. I can tell you any number of people who are in possession of books that belong to me. (If you are reading this and you have my John Updike, Gertrude and Claudius or Leif Enger's Peace Like a River then yes, I am talking to you.) I had to wait a dozen years to get my copy of Hondo--not the Louis L'Amour cowboy novel but a biography of Hondo Crouch by his daughter Becky--and I only got that one back because I saw it on the bookshelf at the home of the guilty party and stole it back.
I'll also admit that I am a book thief, but not without guilt. After reading Louisa Mae Alcott's Little Women, I was ready to read Little Men. My great grandmother had a copy she had borrowed from a friend who died before she returned the book. For some reason, I didn't read her copy but instead borrowed a copy from a friend's brother. He too died while I had the book. Coincidence? I don't know. But I'm not lending a copy to anyone.
Actually, I try to practice book amnesty regularly, giving back books to the friends to whom they belong, not admitting whether I've read them or not. This clears room for more books too.
Meanwhile, I've realized that one of the few drawbacks to reading eBooks is the inability to share them. I always feel guilty recommending a book to a friend, who asks, "May I borrow it?" I have to admit that I don't have a copy to share. Fortunately, this isn't enough of a drawback to deter me. After all, they have the option of buying the book or using the old library card.