Some companies gave describes reasons to go into cloud:

ManTech’s

ManTech’s objective was to be able to quickly virtualize their test and development environment. They focused on two specific challenges - service management and the ability to provide the developers a easy to use interface for requesting resources for their development project.,

SK Telecom

Provide Development Platform-as-a-Service to Business Partners to quickly test, develop, and publish new end-user focused WAP services on SK Telecom network. Reduction in devel- opment time, achieving faster time to market Efficient management of resources, delivering reduction in capex & opex

Cloud computing is a new way to use and deliver IT services that is driven by consumer Internet trends. The cloud computing model builds on the maturation of the World Wide Web, combining rapid scalability, proliferation of the Internet and Internet-connected devices, unprecedented self-service, and the emergence of elegant web-based applications. The cloud allows users to execute complex computing tasks without the need to understand the underlying technology

Cloud computing is emerging at a critical time for the IT industry. There is a growing realization that physical and IT assets, systems, and infrastructure are fast reaching a breaking point. As the pace of business and society in general continues to accelerate, the physical and digital foundations on which progress depends are straining to keep up because of the following factors:

• The explosion of data, transactions, and digitally aware devices is straining existing IT infrastructure and operations.
• Exponential growth in communications subscribers and services is showing limitations in network bandwidth and storage capacity.
• Supply inefficiencies and demand spikes are putting pressure on energy and utility systems.

The emerging cloud computing model, a key part of the Smarter Planet™ vision articulated by IBM and embraced by others, uses improved technologies. This cloud model is characterized by innovative Internet-driven economics that use the massive underlying ability of the technology to scale. Cloud computing offers the vision for improved service (not just high availability and quality of existing services) but also meeting expectations for real-time access along with dynamic access to innovative new services. Cloud computing also allows for reducing cost, not just containing it, but achieving breakthrough productivity gains through virtualization, optimization, energy stewardship, and flexible sourcing.

Of course cloud computing does have its challenges. The complexity of cloud computing, with its increased dependence on Internet, virtualization, and on-demand enabling technologies, requires critical attention to performance and capacity considerations throughout the design, delivery, and management of cloud-based solutions.