A network with twice as many users isn't twice as valuable — it's four times as valuable

Robert Metcalfe, co-inventor of Ethernet, observed that the value of a communications network grows roughly with the square of the number of people connected to it, since every new user creates a potential connection with every existing one. The same logic explains why it's hard to dislodge a dominant social network or operating system once enough people are already using it.

— Robert Metcalfe, Metcalfe's Law — Formulated in relation to Ethernet, 1980s