Once you move your core applications into a cloud-type scenario, all you really have as an interface is a Web browser, which makes access control and password management and identity management incredibly important. You’re not securing pieces or chunks of the network anymore. You’re securing the end user—how they access the network and what they do once they’re on. You’re really entrusting the provider with a lot—make sure that they can provide best practices for access management and identity management.
Phil Hochmuth, senior analyst at research firm Yankee Group as quoted in Public clouds, private clouds and your security