The paper studies the behavior of the Web Services deployed on the cloud, and investigates their performance and the instability of the underlying communication medium. Our result shows how these two factors affect the dependability of cloud-based Service Oriented Architectures (SOA). This study is based on our experiments with the Web Services which were deployed and run on Amazon. We deployed the same service on several Amazon locations and analyzed variations in the response time and the ratio between delays and standard deviation of the average values.