Dave and I will sometimes chat in the office about this '12 and 150 theory' and I thought I would finally write about it and see if others had any feedback.

Gladwell has written about how the military has settled on 150 people per 'company' to ensure that "orders can be implemented and unruly behavior controlled on the basis of personal loyalties and direct man-to-man contacts".   He also mentions that some companies like Gore-Tex have used these guidelines to build an effective organization.  

Gore doesn't need formal management structures in its small plants - it doesn't need the usual layers of middle and upper management - because in groups that small, informal personal relationships are more effective.  "The pressure that comes to bear if we are not efficient at a plan, if we are not creating good earnings for the company,  the peer pressure is unbelievable." 

If 150 is the ideal size to prevent "unruly behavior" then there might be a ideal team size for smaller subdivisions like a military squad where more detailed interaction is necessary.  This number seems to be around 12.

We have seen this pattern repeated in various team sizes.

• Basketball: 12-15 active players on a team
• Soccer: 11 players on the feild
• US Jury: 12 jurors
• Baseball: 10 starters (AL Rules, Go Yankees! ok, this one might be a stretch..)

I have read one theory that connects these sizes to the nomadic, hunter/gatherer origins of humans where tribes and clans were roughly these sizes.   Our brains might be wired to only "completely trust" 12 people and be best at remembering about 150.