Will Cheap Energy Lead to Blowing up the World?

The above question was asked at Marginal Revolution (seen via TJIC):

In Cleveland I posed a variant of the following question: let's say that you can blow up the world if a) you can exceed 1550 on your two main SATs, b) you are willing to spend $50,000, and c) you sincerely wish for world destruction for one month straight.

How long would the world last?

We may someday envy the problems we have now.

I doubt if cheap energy will destroy the world. (By “world,” I mean civilized society in general and not just the mudball we currently live on. Right now, the world is smaller than the Earth but that won't always be the case.) Cheap energy will also mean cheap mass and that can act as protective armor.

For example, the World Trade Center attack involved an energy release on the same order of magnitude as a small nuclear bomb. There's another way to look at this: A structure took a small nuke and nearly survived.