The Dunbar Number Explained

from The Social Brain

Years ago we launched a Facebook group for 100 social-entrepreneur friends.
In the beginning it was magic—funding leads, job openings, rapid-fire answers to tough questions.

Then the group became too popular. Membership surged past 10 000 and the signal drowned in noise. Helpful threads gave way to self-promotion, lurkers outnumbered doers, and replies be…