Little scares the C-suite like shareholder activism. Bosses stay awake worrying about a call, a letter or a 100-page presentation in which a hedge fund outlines the depths of their ineptitude. At the start of the year executives were especially on edge. During this year’s annual “proxy season»—a succession of shareholder meetings—they have mostly avoided votes on dissident nominees to their boards. Nevertheless in recent months some of the world’s largest firms—including Alphabet, Bayer, Disney and Salesforce—have had to tussle with activists, who are increasingly focused on the biggest companies. A battle between Carl Icahn, a prominent activist, and Illumina, a genomics giant, is set to come to a head on May 25th.