Little Free Libraries operate on a give-a-book, get-a-book honors system. Such a nice idea...for nice people.
Rick Brooks, one of the founders of LFLs, has said that, "Everybody asks, 'Aren't they going to steal the books?' But you can't steal a free book."
But considering that just yesterday, in a not-so-little but just-as-free library, someone threw a lit cigarette in the book drop and someone else wreaked havoc in the restroom by shoving an entire roll of tissue down the toilet, taking a giant dump on top of it, and then flushing, well...trust me, free book or not - they'll find a way.