There’s a moment in the 1967 film The Graduate that has become renowned. At a party thrown by his parents to celebrate his graduation, Benjamin (Dustin Hoffman) is approached by Mr McGuire, an elderly bore who wants to say “just one word” to him: “plastics”. “Exactly how do you mean?”, asks the hapless Ben. “There’s a great future in plastics,” says McGuire. “Think about it.” Listening last week to the spending plans of the techlords who run Microsoft, Alphabet, Amazon and Meta leads one to wonder if something analogous might have happened to them on their graduation nights. Except that...