The Smithsonian's SmartNews has a story about stone piles. The stone piles used as markers are sometimes referred to as cairns. For many years, cairns have been used to mark a memorial or landmark. Now, some conservationists are recommending that people stop making markers by stacking stones. The practice is causing environmental damage with erosion and potentially sending people in the wrong direction.
For High Country News, Robyn Martin writes that there is an annoying plague of rock stacks balanced carefully atop one another in the West.
These piles aren't true cairns, the official term for deliberately stacked rocks. From middle Gaelic, the word means "mound of stones built as a memorial or landmark." There are plenty of those in Celtic territories, that's for sure, as well as in other cultures; indigenous peoples in the United States often used cairns to cover and bury their dead. Those of us who like to hike through wilderness areas are glad to see the occasional cairn, as long as it's indicating the right way to go at critical junctions in the backcountry.