Uh.. <raises hand> I might be one of the few people who actually knows a bunch of the theory on why wikipedia works (properly). I had to do a bunch of research while working on wikipedia mediation and policies stuff, a long time ago.
I never got around to writing it all out though. Bits of it can be found in old policy discussions on bold-reverse-discuss, consensus, and etc.
I guess the first thing to realize is that wikipedia is split into a lot of pages, and n_editors for most pages in the long tail is very very low, so most definitely below n_dunbar[]; and really can be edited almost the same way wikipeida used to be back in 2002. At the same time a small number of pages above n_dunbar get the most attention and are the most messy to deal with.
Aaron Swartz actually did a bunch of research into some of the base statistics too, and he DID publish stuff online... let me look that up...
http://www.aaronsw.com/2002/whowriteswikipedia/
and especially
* http://www.aaronsw.com/weblog/whowriteswikipedia
[*] https://en.wikipedia.org/wiki/Dunbar%27s_number (note I'm using lossely in empirical sense, where an online page might have a much lower actual limit than 150)