Economic and business considerations have persuaded businesses to move to the next level of productivity with economically valuable features such as extensibility, agility, elasticity, and security. Availability of such a resource removes the constraints from maintaining an in-house infrastructure (Hardware, Software, and IT manpower) and, therefore, brings in great business value. It also enables businesses with meager resources to concentrate their effort in developing their business rather than getting concerned about the resources.
The "Cloud" vendors aggregate all their resources at data centers, which they can maintain and make them available to businesses on a subscription basis. Recognizing early on, the importance of this cloud-based business paradigm, companies such as Amazon.com (http://aws.amazon.com/); Google (http://www.google.com/apps/intl/en/business/index.html); SalesForce.com (http://www.salesforce.com/) and a few others jumped into this business model and implemented applications offered from the cloud. Although all of them were 'Cloud' offerings, they meant different things as seen in their implementation. The single feature that is basic to all implementations in the cloud is the highly flexible, highly agile, highly virtualized (Servers, storage, and many more), and automated hardware capable of being created on the fly with a high degree of redundancy accessible by a very fast network.
As seen recently, businesses have started liking the flexibility of cloud services related to optimum resource utilization with virtually no overheads; with minimum support personnel and, therefore, smaller payroll expenses; smaller real estate commitment, and the ability to rescind in case of an emergent economic or financial crisis. One of the factors that still deter businesses to go all out for cloud computing perhaps, is security concerns.