Treated myself to an afternoon of stone balancing.
Had a nice chat with some folk from Vermont, who told me about Inookshooks. I see why he thought they were a bit similar, but I wasn't aiming to make an anthropomorphic figure, or even leave a lasting mark on the landscape. I'm aiming to make it look really delicate, so it's fairly unstable, not a quality you'd be looking for in a waymarker.
I do quite like the idea though, of leaving a balance standing so other people can take away whatever message they like from it-but the urge to add just one more rock is usually too powerful. Every one I did yesterday eventually had a catastrophic collapse. They'd have been an OK size to leave too. Not too near a path and not really heavy or tall enough to hurt anybody.