You can tell when an industry trend starts hitting the wall: Salespeople stop talking about it. A few sources have told me that, these days, when customers get a sales pitch that leads with "the cloud," they reply with a look that says: "If I hear 'the cloud' out of your mouth one more time, I'm going to kill you," or something to that effect.
Ironically, just when the cloud "brand" is faltering, the real-world value of this fuzzy collection of technologies and techniques is clearer than ever.
Just have a look at four distinct segments of the cloud in order of hotness: The private cloud is on fire -- for very good reasons that will be explained shortly. SaaS (software as a service), almost entirely a public cloud phenomenon, comes next. After that are the public IaaS (infrastructure as a service) offerings such as those from Amazon.com and Rackspace -- and finally commercial PaaS (platform as a service) environments for application development. Let's start at the top.
The allure of the private cloud
You can argue that the whole public cloud phenomenon began years ago when CIOs looked at Google's infinitely scalable, resilient infrastructure and said, "Me want some of that." In response, data center managers slapped their foreheads and explained through clenched teeth that Google's infrastructure was purpose-built for a single application -- utterly the wrong fit for the average data center.
Meanwhile, the proliferation of server virtualization began to form the foundation for a different sort of private cloud. Virtualization's combination of vastly improved hardware utilization and quick provisioning has proven irresistible, to the point where roughly half of servers in midsize to large companies today act as physical hosts to VMs. That's a huge shift from dedicated resources to pooled resources.