This paper reports our experience in benchmarking a cloud-based web-service and investigates instability of its performance and the delays induced by the communication medium when measured from multiple client locations. We compare the performance of MS Azure, Go Grid and an in-house server running the same benchmark web service and analyze how the client and service implementation technologies affect its performance. The uncertainty discovered in the network delay affects the overall performance and dependability of cloud computing provisioning and requires specific resilience techniques.