Geocaching and Letterboxing both seem to be kind of neat pastimes. My issue is people who place them in the park I work at without asking permission first. We do allow them, but we have guidelines that must be met for the protection of the park. Too many people walking off-trail in the same spot create erosion problems. When we come across caches or boxes that have been placed without permission, we remove them and attempt to contact the placer. Most of the placers never bother to get back in touch with us, unfortunately.