Users of cloud computing are overwhelmed with choice, even within the services offered by one provider. As such, many users select cloud services based on description alone. In this quantitative study, we investigate the services of 2 of major IaaS providers. We use 2 representative applications to obtain longitudinal observations over 7 days of the week and over different times of the day, totaling over 14,000 executions. We give evidence of significant variations of performance offered within IaaS services, calling for data-driven brokers that are able to offer automated and adaptive decision making processes with means for incorporating expressive user constraints.