Card 1 of 8: Metcalfe's Law
Metcalfe sketched this on a slide in 1980, years before anyone called it a network effect: a network's value scales with the square of its connected users, not linearly.
Milgram's 1967 mail experiment asked strangers in Nebraska to route a folder to one specific Boston stockbroker using only people they knew personally. It usually took just a handful of hops.
Granovetter's 1973 insight flipped intuition: your close friends are not your best source of new opportunities — your acquaintances are.
Barabási mapped the web in 1999 expecting a bell curve and found a power law instead: a handful of pages have millions of links, most have almost none.
Dunbar correlated primate neocortex size with group size and predicted human groups stabilize around 150 — the largest village that still runs on gossip instead of formal structure.
Metcalfe counted connections. Reed counted groups. His 2001 addition: the number of possible subgroups in a network of n people is 2ⁿ, which is why group-forming tools — mailing lists, subreddits, Discord servers — can become explosive once they cross a threshold.
Merton noticed in 1968 that already famous scientists get disproportionate credit for joint work — the same result by a newcomer gets ignored. Price and Barabási later showed networks grow the same way.
Granovetter asked in 1978 why two crowds with the same average willingness to riot behave oppositely — one riots, one doesn't. The answer is not averages but thresholds: who needs one other person to join, who needs ten.