Although I do not go out of my way to offer the loan of a book in most instances, I do like to share them with interested individuals. My parents and in-laws are my most frequent borrowers. Whether it's by the bag or box or just a few here and there, it's almost a tradition between us to swap, trade and borrow/loan books between each other. There are a couple of other people I sometimes loan books to as well. While it is my hope that the book will come back (when it's a loaner, I try to make that clear to the borrower), I do not expect it. And so, I have a tendency to loan my favorites out only to a handful of people I know will return them. If my not so favorites (good books and ones I'm not ready to part with that are not among my favorites) do not find their way back to me, it is not something I get excited about.
I do expect the books I lend out to come back in a similar condition to that which I loaned them out. I expect a little wear and tear, but not so much that the book looks like it was splattered with coffee or pizza sauce, pages were ripped out, the cover torn, etc. Only once has someone returned a book to me in that awful condition with no apologies or excuses and that was the last time I loaned that person any of my books.
I do borrow from other people, mostly family and sometimes a friend or two. I am terrible about holding onto books loaned to me for long periods of time. While with my family I can argue distance, the truth is that I do not always make it a priority to read the books. If the mood does not strike me to read a particular book, it can sit on my shelf for quite a while. This happens more so with family loans. With friends who live close by, I tend to be quicker about the turn around, and will either return the books unread or read them within a decent amount of time. Sad to say, they often get returned unread. I finally gave up bookrings and bookrays through BookCrossing because I find myself passing the books along unread more often than not these days.
My disclaimer to anyone who offers to loan me books is that I am slow about returning them, but I will return them. I have even refused loans of books I really want to read because I know I will not be returning them in a decent amount of time.
On occasion I have loaned a book to someone, and it hasn't found its way home. The Curious Incident of the Dog in the Night-Time is still out there, for example. It's been a couple of years now. In an e-mail recently, my friend told me she still has the book, something I was sure she must have forgotten about by now.
As for me, I do return books to their rightful owners. Do unto others and all that. My mom knows to tell me which books she wants back and which I can send on to my mother-in-law. I keep a list of the books loaned and who the lender is just to make doubly sure I do not forget. So, while you can be assured I will return your book, my biggest flaw is the length of time it takes me to return it.
What about you?