Buzz says: "..having a library of books that you have read is like keeping a six-pack of empty beer bottles. I have come to give away the books that I read so that others might enjoy them".
As a result of the recent burglary, I've just started to put all of the books in my library into an Access database. I've spent 15 years building up a library of books that shaped my brain and they mean a lot to me. Not only because I like to refer to them regularly, but because I hope someday they will be a source of education and inspiration for my kids. If they were ever stolen, or lost in an accident, it would take years to replace them. Many are first editions, some Napoleonic histories 200 years old, etc. I've got shelves full of books, must be somewhere near 1000.
So I don't lend them out, but I do often give copies of some of my favourites as gifts to people I care about. Recently I've given away books by Ayn Rand, Noam Chomsky, a biography on Napoleon by Vincent Cronin, and a Rimbaud. I like to give people books that changed my view of the world. I'm not much into fiction, unless it is fiction with purpose.