K. Scott Morrison had an interesting blog post about cloud computing, SOA, and the emerging use of private clouds.
"Private clouds represent an opportunity for orderly transition. Some would argue that private clouds are not really clouds at all, but I think this overstates public accessibility at the expense of the technical and operational innovations that better characterize the cloud. Private clouds are important and necessary because they offer an immediate solution to basic governance concerns and offer a trustworthy transition environment for people, process and applications."
The fact of the matter is that private clouds are a clear, and rapidly emerging architectural pattern. This is not only around the security and control issues that are driving many to keep their clouds within their own data centers, but the fact that using private clouds just makes good architectural sense within many enterprises.
Private clouds had a bit of a rough beginning. Most considered cloud computing an "over the Internet" concept, and thus calling something a "cloud" that was in your data center, seemed a bit silly. However, as the value of public clouds were proven, including on-demand provisioning and scalability, the architectural pattern of public cloud computing just made good sense for use within the enterprise when systems had to remain on-premise.
Another important thing to consider is the use of SOA. Since cloud computing is best addressed using SOA, so are private clouds. Indeed, in many instances private clouds are an enterprise's first use of SOA approaches, and while SOA is not cloud, it will clearly get you to cloud.
Interesting times ahead.