Identifying the closest fog node is crucial for mobile clients to benefit from fog computing. Relying on geographical location alone us insufficient for this as it ignores real observed client access latency. In this paper, we analyze the performance of the Meridian and Vivaldi network coordinate systems in identifying nearest fog nodes. To that end, we simulate a dense fog environment with mobile clients. We find that while network coordinate systems really find fog nodes in close network proximity, a purely latency-oriented identification approach ignores the larger problem of balancing load across fog nodes.