This document discusses the evolution of cloud computing from mainframes in the 1970s to modern cloud platforms. It covers the core models of cloud computing (IaaS, PaaS, SaaS) and shows that cloud adoption among large enterprises has reached critical mass. Analyst reports from 2008-2009 find that early adopters are seeing benefits, and most enterprises will use cloud services over time. The document also discusses workload patterns well-suited to cloud services and reasons for considering a cloud-based approach.