I call it the Turing Chaos; intrinsic to computer science is that a single bit flip can completely and utterly change how a system works... and this is not a trivial observation, it is actually a deep and profound observation about the difference between the "cyber"world and the physical world that has pervasive and radical consequences at every level from the entirely ivory-tower theoretic out to how Grandma uses her computer (as you mention). Usually I've thought of this in the context of programming in general and trying to contain bugs against the overwhelming forces of chaos pressing in on us as we try to build systems of millions, billions, or trillions of bits; as programmers, we are exposed to some fairly raw mathematical chaos, in the "chaos theory" sense of the term, and in particular, the difficulty of fully predicting what a chaotic system will do in response to some stimulus. A great deal of software engineering is a desperate attempt to wall it away from ourselves and confine our intrinsically wild and wooly systems to just the behaviors that fit in our heads... but alas, we fight against a crafty foe that can find even one bit's worth of weakness and bring millions of dollars worth of systems down around our heads.
And that's before we consider human attackers.
One bit flipped can be the difference between an attacker walking off with the entire contents of your billing database, or getting a simple rejected request. One click can start a cascade of trillions of instructions terminating in your amazing computer becoming a spam delivery device that belongs to a guy 15,000 miles away. Every computer program stands balanced precisely on a small, small knife edge, with an n-dimensional abyss waiting on all sides to consume it, and hostile, intelligent forces anxious to give it a small, carefully calculated tip into their bit of it.
That probably doesn't work for the essay you're looking to write; my metaphor comes more from the software engineering side. But I think it's the same thing; the computer world is the math world, and it is a harsh, subtle, uncompromising place compared to the physical world, no matter how complicated the latter can be.