Abstract
Topological states of light can possess interesting properties, such as strong light localization and robust waveguiding, with promising applications in lasers, integrated optical chips and other photonic devices. For these applications to materialize, it is necessary to understand the precise limitations and possibilities of photonic topological states and devices. In this critical evaluation, we highlight the approximate nature of topological protection in photonic systems and discuss the circumstances in which this protection can, and cannot, play a useful role.