As soon as I saw the title, I knew Nick Bostrom would be involved. And therein lies chaos.

First, to clarify something from the article - Bostrom's "posthuman" civilization is not strictly about the singularity but about almost unbounded capabilities. Building computers out of planets would be within reach for such a civilization. Think Culture, not Neuromancer.

The ratio of simulated people vs people in the actual universe was "addressed" in one of Bostrom's subsequent papers but in a completely ad hoc if-you-do-this-then-you-prove-my-point way. Here's some arguments against it - http://rationalwiki.org/wiki/Simulation_argument#Calculating...

All in all, the SimArg is a nice thought but it's so easy to poke holes without first becoming a posthuman civilization that it loses what little stability it might have had.