This weekend included software failing because of bugs handling the leap second correctly (thanks tidal friction!) and disrupting many popular sites with it. A single change that feels small was able to shatter what had previously felt so stable.
That property has always fascinated me about software. In one momement software can feel like it is made of steel, silently cranking away. You have the feeling it would work for the next 1,000 years if you went away. (Of course, it wouldn't; software decays.) And in the next moment it is on pieces on the floor. Or you find a bug that makes you question "how did this ever work properly?"
This mixture of strength and fragility don't seem to have a simple analogy in the physically constructed world. Buildings don't abruptly crumble, bridges rarely just fall down. It leads me to think that the sense of solidity is at least partially an illusion. That software is less resilient to change and new conditions than we hope, and is in a world in flux.