The rise of worldwide Internet-scale services demands large distributed systems. Indeed, when handling several millions of users, it is common to operate thousands of servers spread across the globe. Here, replication plays a central role, as it contributes to improve the user experience by hiding failures and by providing acceptable latency. In this paper, we claim that atomic multicast, with strong and well-defined properties, is the appropriate abstraction to efficiently design and implement globally scalable distributed systems. We substantiate our claim with the design of two modern online services atop atomic multicast, a strongly consistent key-value store and a distributed log. In addition to presenting the design of these services, we experimentally assess their performance in a geographically distributed deployment.