This topic has been addressed before, but only from a lending perspective I think, so yes, chat away people, do you lend/borrow, and if you do one, do you NOT do the other? I'm curious about that myself.
I personally tend not to lend, I just buy new copies for other people Or, give mine away for keeps. I rarely borrow, and I'm sure I've poor ole Gyre driven demented as I have one of her books with ages!