I have never understood why folks are “anti-cairn.” If hikers want to use something from the natural landscape to help mark their trail and that helps prevent someone from getting lost, then that is fine by me. The National Park Service and National Forest Service routinely use rock cairns to mark off trail routes in order to help prevent folks from getting lost (Mount Langley above Old Army Pass and the south side climbers trail on Mt. Adams in Washington are two good examples where the park/forest service has created quite immense rock cairns to mark the route). I once saw a San Gorgonio Wilderness trail volunteer knocking over cairns on the San Bernadino Peak trail, and I wanted to throttle him for his stupidity. Purposefully doing that and increasing the chances someone might get lost wass a dereliction of duty in that case, at least in my humble opinion. If somone is using ribbon or wands to mark a trail, then they should certainly remove those on their way out (most people do with wands, though I have seen ribbon tied to trees in cases when I was pretty sure those who had used it to mark the trial were long gone from the trail).