NO. Cloud Computing is not SaaS, and SaaS is not Cloud Computing. Cloud computing incorporates SaaS, and that's it. I believe the OP is referring to "calling a method over there from over here." That's not what cloud computing is. I stand with Larry Ellison on this one. "What the HELL is cloud computing?!".
Cloud computing is creating an application and throwing it "up there" instead of serving it from a dedicated server. Sharing resources, and location independence. So, I guess cloud computing REQUIRES SaaS. Cloud Computing for Microsoft.NET is NOT called WCF as someone above said, Azure is the framework for could computing in .NET. And it's still a beta. Please, don't get me started on cloud computing.
