Digital business leaders face a dilemma: What made their firms successful in the past is now holding them back. Incumbents boast an existing customer base and brand pedigree but are saddled with the crushing inertia of scale. Startups bring agility, pace, and a devil-may-care attitude — and threaten to overturn markets. Forrester interviewed a range of digital disruptors, all founded since 2009, to understand how they operate and what incumbent firms can learn.