Some groups really are much less hierarchical than others, though. Think kids in middle school/high school at one end of the continuum and flat-structured silicon valley startups at the other end. (Paul Graham: "I never had to manage anyone in our startup, even though I was the president. The other hackers were my peers, and would have given me the raspberry if I'd tried to "manage" them. We operated by consensus.")
Maybe as you get to be Google/Facebook-sized there's more pressure for hierarchy to develop?
http://www.meltingasphalt.com/the-economics-of-social-status/
Discusses a number of aspects of social status, including the "social status as currency" concept that Morendil and I previously wrote about.
But the part that I found the most interesting was the idea of defining communities via their status standards:
The article has a lot more.