Not necessarily -- you can have the really big decisions made by consensus in a horizontal fashion while still delegating much of the decision-making power. No one's arguing that everyone in the organization sit down for every decision. There's no need for everyone in the organization to sit down and decide whether candidate X is a good hire (though that might work just fine for really small teams). Delegate as much authority as possible to the actual experts in the domain and the stakeholders of that decision. As decisions affect more and more people, figure out ways to involve everyone in that decision making process in a horizontal rather than a vertical way. Asking "Who's responsible making sure the code is high quality and we're not taking on too much technical debt? or "Who's responsible for making sure we're in legal compliance?" or "How are you going to resolve a disagreement about which vendor to use for XYZ" is a different question entirely than "Who's in charge of everything?"

I guess Buffer comes close enough.