Hedge funds that want to scale up and diversify as their fees come under pressure and investors flee the $3 trillion industry should follow Amazon.com Inc.’s growth strategy, according to Balyasny Asset Management. Dmitry Balyasny, who leads the investment firm, says the mail-order giant has crushed the competition by relentlessly investing in its business, expanding into new areas, hiring the best talent and exploiting its pricing power. “While it is unlikely that any hedge fund is going to compete with Amazon for the title of ‘World’s Most Valuable Company,’ we can learn a lot from their strategy,” Balyasny wrote in his first-quarter...