Sometimes with the shoes, it's obvious that they have outlived their usefulness to one person and have been put out to be found and used by another person.  Other times, I'm not so sure.  Sometimes I'll find a pair of shoes under a bench that look like the person took them off while they were sitting and reading and then walked off in barefeet, forgetting that they had come in shoes.  The other puzzle is when I find single shoes.  What happened?