[ZenGum]

Very acute thinking here. We have wound our societies up to near maximum optimisation. We have awfully little redundancy in case of mishap.
It applies at most levels - people's finances, companies running on just-in-time inventory, cities with only a few days worth of food in them.
This year a dinky little volcano is Iceland shut down a big chunk of global air traffic; strange consequences rippled around the planet. There are dozens of potential hazards much worse than some volcano no one can pronounce - solar storm, asteroid, plague, nuclear exchange, or even just a coincidence of minor glitches at crucial places like oil refineries.

I probably shouldn't think about this too much.