You had to look hard amid the four-foot floral sculptures and the Vera Wang originals to see signs of the economy’s collapse at the International Debutante Ball at the Waldorf-Astoria on Monday night. There was the daughter of the Duchesse de Magenta, Pélagie de Mac Mahon, a willowy 18-year-old with chestnut hair who is a great-great-granddaughter of a 19th-century French president. And there were the two sisters from Hong Kong, daughters of a heart surgeon and a jewelry designer, who stayed not two nights but two weeks at the Waldorf, passing the days on the lookout for designer dresses. Champagne...