The ultimate authority is the owner of the means of production, Jimbo Wales, an Ayn Rand-worshipping millionaire and porn magnate. Under him are his lieutenants, administrators and bureaucrats (that's what they're called on Wikipedia). Then there's normal users. There is a distribution of power, but the admins/bureaucrats have more than regular users, and Jimbo has ultimate authority. My inability despite fighting since 2003 to get the Khmer Rouge article to adhere to the supposed neutral point of view of Wikipedia are a testament to this. I am being completely rational manner, acting like I'm publishing a peer reviewed paper, while the other side is completely hysterical. The Israel/Palestine section is like that as well, although I've never dabbled in it.
To answer your question in another way, I am reminded of that X lyric "this is the game that moves as you play". The rules on Wikipedia change day to day. I actually was (inadvertently) instrumental in getting the "no more than three reversions a day" guideline changed from a guideline to a hard-and-fast rule. Wikipedia has a crappy (and slow) judicial system.
I suggest people use Anarchopedia and/or Chuck0's Infoshop Openwiki (or Demopedia, Dkosopedia or Sourcewatch which focuses on lobbyists) for anything pertaining to history, economics and whatnot. Wikipedia is only good for stuff like hard sciences in my experience. I still edit there but not as much as I used to, it's not worth the effort, I've given up on it. I mean, I've been fighting over one article since 2003. What's the point? It's better to do it on another wiki without the Fox News crowd mucking with your article, like the ones I mentioned.