"Plus you only pay for the server time you use," Cord sayd. "Mainframes are back!"

If the cloud behaves more like an operating-system platform—providing the primary interface through which customers access their applications, virtualization is clearly a key part of the equation and a tremendous benefit within the cloud, according to Charles Kinnan, a software architect and founder of Milyli, a new company working on rich Internet applications for product lifecycle management.

"[But] it doesn't seem like this is the way that clients for the cloud are moving," he says. "With the variety of devices, screen sizes and input methods 'they' are touting for the cloud, chances are better that client software will still run on the devices and be tailored for each device with the data being sent up and down to the cloud.

"So many new Web-friendly, client side platforms are becoming popular—Adobe Flex and Silverlight for PCs, Android for phones, etc.—it would seem to me that most cloud computing will rely on client software connected to data storage services."

Within the data center—assuming predictions are correct that data centers will evolve into ultra-high-density server farms packed with lower-speed processors among which applications can be shifted freely—trying to manage a single OS connected to a single user would be a nightmare.

So a good degree or automated provisioning of virtual servers would make a lot of sense," Kinnan says.

In short, he sees cloud computing server farms becoming 'plug and play data centers.'

In the long term, there's little concensus of how the uber-trends toward virtualization and cloud computing will mesh, and how smoothly. Still, while virtualization isn't absolutely necessary for cloud computing, it certainly will help.

© 2009 CXO Media Inc.