but in a large building / campus, they can't possibly monitor electricity usage per individual or company occupying the space without upgrading the infrastructure significantly.

And things like a class of students sitting in a lecture theater with their laptops plugged in, are they mining or gaming or maybe just some hung process is in an infinite loop taking the CPU to 100%?

(I'll admit that I've used a "heater.exe" for warming my hands with a laptop on a cold day...)

I'm imagining a future where every 'public' power outlet has a credit card reader attached.

You mean a bitcoin interface, surely :-)

That sounds like an infinite loop waiting to happen.

Imagine a world of digital sustenance miners.

Just because you won't get caught doesn't make it right.