Is it a new paradigm?
Why wouldn't we view the move to the cloud as the understanding that things are different today, and it is no longer appropriate to try to think about "centralized" systems in any way? It seems to me that the major lesson of where we are today (software eating the world, cloud, BYOD, consumerization of IT, demand for 24/7 tailored services for all) is that we should be embracing our new distributed world. Each department can select and own its SaaS, because service providers take control of what IT used to, and because employees are increasing tech-savvy.
Isn't the real answer to the "silos" that are created by cloud the Enterprise Service Bus (ESB)? Where our model is distributed systems, but that we build a bus that allows interaction? Think of how SAML is so standard that AWS ultimately had to build support for it into their API (what other interoperability APIs has AWS built in?)
The IT department of the future is one that sets guidleines, not tries to regain command-and-control of everything that happens through the enterprise. "Our email is hosted by X provider; as long as you pick a mail client that supports multi-factor authentication with X, you can use that mail client." "You may select any payroll SaaS, as long as it supports SAML."