IT adopts technology and new approaches conservatively. After all, the lights have to stay on, revenues have to come in and the day-to-day business of the organization has to continue even though something new is being brought in. I've seen some really unbelievable stories and posts describing a near future world in which all organizations are using virtualized systems for every task or cloud computing for their basic infrastructure that remind me of similar stories about different technologies in the past.
After all, organizations have a different set of goals and different requirements for each workload. Some have to execute as fast as current technology will support. Others need to scale up to handle the largest number of people. Quite a few workloads just need a very reliable execution environment and running on one of today's systems provides more than adequate performance.
Those who have watched the world of IT for a while learn that IT seldom makes sudden fundamental technology changes on every system, for every workload, everywhere. all at the same time. It's just too hard to keep things running if everything is changing rapidly. There's simply too much to do to move all tasks and workloads from one type of technology to another without having something die in disgrace in the process. No, IT decision makers live by the golden rules (see Reprise of the Golden Rules of IT) that are based upon decades of learning while technology has advanced in every direction.
New technology tends to be brought in and runs along side of older technology. The older, established technology continues to run as long as needed. Virtualization technology, long a mainstay in the world of mainframes and midrange systems, is starting to be seen as a foundation of many tasks hosted on industry standard systems. That being said, hosting applications or application components on physical systems hasn't stopped. The same is likely to be true as cloud computing becomes part of an organization's IT infrastructure.
Cloud computing is still in one of the early stages of the hype cycle. We're all likely to read stories pointing to a single instance that declare that everyone and no one will move in the direction of cloud computing. What's more likely is a gradual adoption that is based upon an organization's own needs and upon its own time frame.