-- Fully virtualized. Nearly every cloud computing vendor abstracts the hardware with some sort of server virtualization. The majority employ a hypervisor to keep costs low. Some have solutions that span virtual and physical servers via another middleware element, such as a grid engine.

-- Equipped with dynamic infrastructure software. Most clouds employ infrastructure software that can easily add, move, or change an application with very little, if any, intervention by cloud provider personnel.

-- Pay by use. Most clouds charge by actual use of resources in CPU hours, gigabits (Gbs) consumed, and gigabits per second (Gbps) transferred, rather than by a server or with a monthly fee. Their pricing is compelling.

-- Free of long-term contracts. Most cloud vendors let you come and go as you please. The minimum order through XCalibre's FlexiScale cloud, for example, is one hour, with no sign-up fee. This makes clouds an ideal place to prototype a new service, conduct test and development, or run a limited-time campaign without IT commitments.

-- Application and OS independent. In most cases, the architectures of clouds support nearly any type of app a customer may want to host as long as it does not need direct access to hardware or specialized hardware elements. Cloud vendors told say there's nothing about their infrastructures that would prevent them from supporting any x86-compatible OS.

-- Free of software or hardware installation. You tap into a cloud just as you would any remote server. All you need is a log-in. There's no software or hardware requirement at the customer end nor the need for specialized tools.

"Gartner likes to describe cloud computing as Infrastructure-as-a-Service (IaaS) model. Cloud computing extends the existing capabilities of IT by offering infrastructure or platform-related services on a subscription model. It is a concept that provides computing resources residing on external devices connected to a mesh of grids, allowing the users to deploy their applications or outsource their functions through the Internet without being aware of the whereabouts of the physical infrastructure," says Staten. What's significant to note is that unlike utility or on-demand computing, the provider is in complete control of the infrastructure. This translates easily into a kind of service, which enterprises can leverage and use without significant internal expertise and hassle to control the supporting infrastructure.

Here's an example from Staten. "When an enterprise deploys a new app, it is the role of its IT shop to figure out where to fit it. The queue to get an app implemented is anywhere between four weeks to nine months. If someone in marketing wants to launch a new promotion, they can't wait that long. They would prefer to go to a cloud vendor, and without a lot of technical knowledge, they would get their app loaded and available, and would pay for it with their credit cards."