You don't need strict hierarchies, necessarily (in fact I don't believe 'traditional' hierarchies are in practice ever actually ironclad: the org chart is only ever an approximation of the real power structure). It's more that you should plan your power structure carefully (many forms are possible!), and ideally make it as transparent as possible, as pretending that you won't have one at all is merely an illusion (you will never completely succeed! Firstly because power structures are, in their full glory, ludicrously complex and ever-shifting, but also because hidden information is itself a form of power)