Searching the photo sharing sites, not much info on these piles and I am too lazy to register and send messages to the authors.
(This is a good one. I can tell it is out on a lava flow, perhaps in the western US? Nah, it is in Hawaii. Note these little piles are not in a line along a trail, so they are not trail cairns, in spite of the photographers comment.)
(The photographer identifies this as Stow Vermont. David Lacy are you listening?)
"Sinking Creek to Dragons Tooth AT Hike 1-14 & 1-15-06"
There is more but I stopped after page 12. Check out "Web Shots" photo sharing. That last one is a honey, isn't it?