There has been a great deal of back in forth in the blogosphere around the use of private clouds, which generally means IT infrastructure that relies on the same techniques cloud providers use for their own datacenters, such as multitenancy, virtualzation, Web delivery, and highly standardized environments. Most of the discussion emerged from a blog post by Appirio, "2009 prediction: Rise and fall of the private cloud."

The following comment is what set off the firestorm: "Here's the rub: Private clouds are just an expensive datacenter with a fancy name. We predict that 2009 will represent the rise and fall of this overhyped concept. Of course, virtualization, service-oriented architectures, and open standards are all great things for every company operating a datacenter to consider. But all this talk about 'private clouds' is a distraction from the real news: The vast majority of companies shouldn't need to worry about operating any sort of datacenter anymore, cloud-like or not."

Of course there were some valid responses supporting the private cloud concept, including this post by beaker: "If we're talking about a large, heavily regulated enterprise (pick your industry/vertical) with sunk costs and the desire/need to leverage the investment they've made in the consolidation, virtualization and enterprise modernization of their global datacenter footprints and take it to the next level..."

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Fact is, the term "private cloud" is a legitimate architectural pattern and option that has value within some problem domains. Typically, private clouds are virtualized architectures that exist within private datacenters but vary greatly in configuration and technology. There is no standard for what constitutes a private cloud.