We had a taxi driver call the stacked stones (a.k.a. wishing garden) "monkey-see, monkey-do." Seems it has nothing to do with Aruban culture or history... imported by tourists. There were only a few over by the natural bridge back in 2009. I hadn't really thought of it as graffiti until now - but that fits - some folks seem compelled to leave their mark. (I suppose it is much prefered to tagging or litter of course.) While the occasional stack can have an artistic quality; enmasse they are strange rash on the landscape.