It's no coincidence that so many big businesses need government assistance and ultimately need to be bailed out. I think in a voluntaryist society you would probably not see such levels of centralisation because they tend towards big inefficient bureaucracies. And the free market tends to punish inefficiency.
Yes; everything government does to subsidize big business would no longer be possible, making it more efficient for local business to flourish, than for one huge business to have a store in every city, some on every other street (like McDonalds.) In this way, the hierarchies go away on their own; since local business does not need to pay the overhead of corporations, they keep more of their profits, and thus are able to pay their own employees better wages.
Not to mention, with low-level work being replaced steadily by machines, it seems we're on our way, as a species, to every job being highly skilled work that only humans are capable of. It seems more important than ever, then, for any economy to thrive, that people not be trained to be mindless workers, but just the opposite, thinking and participating. The hierarchy seems to push this idea, where you have the few who think and the many who work; perhaps this is the natural push for people to take more control of their work, which would make those hierarchies smaller, since the low-level work only becomes more and more scarce.