Identity management is a huge part of any organization's migration into “the cloud.” Sure, you can move your email, your IM and presence, your document libraries, maybe even your voice and video services into Office 365. But unless your organization is very small, identity management will still take place in your own on-premises Active Directory.
Since the introduction of Office 365, and even before that with the ironically named “BPOS,” Microsoft has had several different solutions for cloud identity management. These solutions have ranged from bad to confusing. The solutions that have been easy to use have lacked good functionality, and the solutions with enterprise functionality have been difficult and costly to deploy.