I do actually mention at the end of the post that this likely doesn't scale up to hundreds and employees. But we'll see how it does work over time. So far so good. :)
Well from what I know Valve operates on pretty much the same principles (employee-driven, very flat hierarchy, high inter-team mobility and teams as interest groups more than boxes to put people in), so if you can keep the culture in and manage to only hire good cultural fits it scales at least to 260 (approximative valve headcount when Portal 2 was released)
I was the fifth employee at my current employer, been through two acquisitions, now sitting at 220+ (not all developers). Scaling has been a difficult but rewarding and fun problem to tackle.
And damn, somehow I missed the last paragraph where you covered your ass ;) Thanks for pointing that out.
"Is this workflow going to work for us when we’re 500 employees? Likely not. But core values and ideas last. Figure out what your core values are, and adapt and refine them as you grow."