Valve Software has a similar flat organization structure. You can view their employee handbook on their website[0], which outlines it pretty well(from the inside).
From what I've read[1], scaling of the small development/production groups is the pitfall.
[0]http://media.steampowered.com/apps/valve/Valve_Handbook_LowR...
[1]http://www.wired.co.uk/news/archive/2013-07/09/valve-managem...