Startup hackers should know more game theory. You can explain a lot of human behavior as evolutionary adaptations to compete in partially-cooperative sex-selected games of incomplete information in groups of around 100 players.
For example, why we care about karma on social networking sites, why some employers require you to wear a suit even though everyone concerned thinks suits are stupid, why religions are tenacious, why nobody trusts atheists, why virtually every mid-sized American city has at least one completely uneconomical skyscraper in what passes for "downtown" and why it's always owned by a bank or insurance company... the list goes on and on.
For example, why we care about karma on social networking sites, why some employers require you to wear a suit even though everyone concerned thinks suits are stupid, why religions are tenacious, why nobody trusts atheists, why virtually every mid-sized American city has at least one completely uneconomical skyscraper in what passes for "downtown" and why it's always owned by a bank or insurance company... the list goes on and on.