In a sub-Dunbar organization, co-ordination takes place informally. In a super-Dunbar organization, you need formal communication mechanisms.

From Women Meet, Men Re-org, 1-7 by Arnold Kling.

I learned about meetings at Freddie Mac. I started working there late in 1986, when it had only recently increased in size over the Dunbar number. In a sub-Dunbar organization, co-ordination takes place informally, requiring neither meetings nor a formal org chart. In a super-Dunbar organization, you need formal communication mechanisms.