I've had a few experiences with flat organizations.
Notably, the one which was proud to loudly proclaim it's flatness and openness was far and away the worst. It didn't quite fit the high school analogy, but it wasn't far off.
In reality, the "flat", "open" structure was actually a concentric hierarchy radiating from The Boss. The Boss > The Inner Circle > Untouchables > Loyals > The Rest.
As bad as that was, I'm still inclined to something generally flat given an exceptional leader to set the tone.
How is this different from a traditionally structured office? The Boss is the CEO, the inner circle are the VPs. The Untouchables can be literally anywhere in the org, but generally have special titles, like "Director of Creative Direction". The Loyals tend to be management. The rest are the rank and file.
All this really tells me is, given a lack of formal hierarchy, people tend to organize themselves into the exact same hierarchies that are formalized everywhere else.
Notably, the one which was proud to loudly proclaim it's flatness and openness was far and away the worst. It didn't quite fit the high school analogy, but it wasn't far off.
In reality, the "flat", "open" structure was actually a concentric hierarchy radiating from The Boss. The Boss > The Inner Circle > Untouchables > Loyals > The Rest.
As bad as that was, I'm still inclined to something generally flat given an exceptional leader to set the tone.