There's another thing that is specific to IaaS: auditability. Part and parcel of Oracle's business model is sending goons to count your servers running this or that appserver, and invariably telling you are not paying enough in licenses. A serious cloud-based architecture that can scale up and down at will (which is what you would deploy on AWS) is fundamentally non-auditable, because it can be scaled down to minimal levels when auditors land. But if you're running on Oracle's servers...