[rms]

Energy is fundamentally scarce. I am thinking about much larger scale uses of energy than anything humans are doing right now. Check out the link to the Kardashev Scale posted above, we need orders of magnitude more energy to build something like a http://en.wikipedia.org/wiki/Dyson_sphere

[NSX2]

Okay, I'm talking about energy for a state of practical human affairs, not building a death star / second sun or whatever that thing is.