Exploring a city drain, and I leapt over a puddle, and mid-air I kinda saw something and ducked my head sideways. Turned out I'd leapt directly into a 30cm piece of sharp, rusty reinforcing rod that was hanging out of the ceiling and bent directly toward my eyes. I don't really know how I avoided it, but if I hadn't, it may well have been an instant involuntary lobotomy..
I think they both have two motives: they are ideologues (neoliberal, fascist), and they are self-interested. MOST of the time, those interests align - at least enough to cooperate. But when they stop aligning to the point that any loyalty that exists is strained, then things fall apart.
River rocks will if you get them too hot too fast, because they have water inside, and it boils. Drier rocks are usually OK, they might crack though.