Jaron comes across as afraid of the future. His thesis seems to be that there are many possible horrible futures, and he imagines them to be more likely than "good" outcomes. And it doesn't read like he has any tools to reason about either one or the other. Hence the fear.

Bill Joy went through a similar phase with his infamous grey goo manifesto. I think he has come back somewhat from the brink on that.

I can appreciate the fear aspect of it. Greg Benford's TimeScape [1] scared the crap out me.

[1] http://en.wikipedia.org/wiki/Timescape