One of my other roles is the editor of Facing North, a review site for all things alternative spirituality. Every month or so, I send out a pile of books and things to my group of reviewers.
I have learned to always put a ‘delivery confirmation’ on my packages, otherwise they tend to mysteriously disappear en route. (I once had thirteen, yes THIRTEEN, packages to different people disappear — an entire mailing.) This costs me more money, but media mail is pretty cheap to begin with so I just chalk it up to the cost of doing business.