In their book, Superfandom: How Our Obsessions Are Changing What We Buy and Who We Are, authors and cofounders of toy company Squishable Zoe Fraade-Blanar and Aaron Glazer dig into how some brands manage to turn ordinary consumers into diehard fans. In this edited excerpt, they discuss why Berkshire Hathaway’s annual shareholder meeting is know as the “Woodstock of Capitalism.”