The rise of the platform economy has been the subject of celebration and critique. Platform companies like Uber, Airbnb, and Postmates have been rightfully celebrated as positively disruptive, introducing much—needed competition in industries that have been otherwise over—mature and stagnant. However, some of the leading new platforms have had such meteoric success that their growing market dominance and technical capacity raise questions about new forms of anticompetitive practices, and negative impacts on consumer and employee welfare. In this Essay, we develop a framework for considering the market power of platform companies that use digital technology to connect a multisided network of individual users. Specifically, we use the example of Uber as a lens to identify eight questions that are important for assessing platform power. These questions address the way a range of issues play out in the platform context, including more traditional competition concerns around innovation, regulatory arbitrage, barriers to entry, and price setting through platforms' use of the network form to coordinate transactions, the use of digital pricing, and the use of pricing bots. These questions also focus on new concerns about power derived from data collection and use; the use of data to expand into other markets; and the implications of market power for consumer choice about personal privacy. Together, these questions provide policymakers a framework to consider whether and how questions of market power (and competition more generally) may pose complexity or require analytic adjustments—and how the development of platforms implicates both new opportunities for, and challenges to, consumer and employee welfare in the digital context.