I think if I already had a business of 10-15 people this would be a good model to attempt to follow. If I had a business of 40+, I would be far more wary; the question of scale is for those who may try to fit the model to their existing business.
The assumption when you publish an article is that you're doing it to provide examples to others, not just talk about how good you are. In that situation, I think it's fair to point out the limitations and areas where this strategy might not work.
However, if you want your company to grow into a Groupon or Zynga, and you have the rapidly expanding demand to support that, then you need to scale. I don't think Groupon could run on 26 people, so they needed to scale to get to such massive revenue figures.
I specifically didn't use Facebook as an example because I know your feelings about them. I figured Groupon at least has the revenue to support their valuation :)
You can't "want" your company into becoming a Groupon or a Zynga by design a certain organizational structure. Startups try that all the time by preemptively hiring tons of people to sit around and wait for the hockey stick growth that never comes.
Well let me ask you this. When is it the right time to reorganize and evolve from the flat structure because you are growing like gang-busters and can't keep up with the pressure on all areas of the company (support, development, sales, etc.)