My colleague Michael Scherotter and I had a couple of conversations about CaaS on Michael's Communicating show on MSDN's Channel 9.

The first show contains an overview of CaaS.  This show talks about: the evolution in telecommunications equipment from monolithic hardware and software solutions to applications implementing a Service Oriented Architecture (SOA) on commodity hardware; trends in networking that support CaaS; and the other tenets of CaaS, like multi-tenant software.

http://channel9.msdn.com/shows/Communicating/Communications-as-a-Service-CaaS/

The second show covers the conceptual architecture of CaaS - which is a layered architecture that create a strict separation of concerns between parts of the solution.  This seperation of concerns supports a flexible architecture that is essential to the successful deployment of a CaaS application. 

http://channel9.msdn.com/shows/Communicating/CaaS-Conceptual-Architecture/

I plan on increasing my writing and creating videos on CaaS.  Future topics will include: CaaS and Services Syndication; the infrastructure required to deliver CaaS applications; lessons learned from a CaaS project; and Managing a CaaS environment.