It's been raining here in Northern California for weeks. This is presumably a good thing after such a long drought. The ground is soaked now and it's not only the rocks that are thinking about sliding.
Of course when people choose to 'slide' they do it to have fun. Why would it be any different with stones?
Rocks seem to naturally want to 'gravitate'. When we try to hold them back, or build them up, say in a dry stone wall, are we merely delaying their gratification?