Robin Dunbar, a British anthropologist, developed a theory that the human brain can handle a maximum of 150 social relationships. Thereafter it loses track of the links in the social network, and people become blurred into one mass.
150 became the Dunbar number, and has been subsequently shown to be the ideal maximum size for a company.
Companies with more than 150 staff experience break-downs in internal communication and a change in culture from “family” to “corporate”.
Some companies, like 3M, have a policy whereby no unit may have more than 150 staff. As soon as a division grows past that number, a new unit is created (with new offices and accountants and HR).
The goal is to ensure that each product is run by a “family” team that can exploit the benefits of trust and speed that are made possible by groups of people that know one another.
If you want to maximise communication and culture, keep staff to under 150.