Must do some research before you put your business in the cloud.
Large enterprises have several specific requirements like
1. High level of Security.
2. Knowledge of Physical location for security and audits.
3. Compliance with several standards
5. Applications integration
Due to these requirements its difficult for large enterprises to choose cloud based infrastructure as cloud have several issues.
A dedicated server usually hosts 200 to 300 websites however when it comes to cloud 3000 to 5000 can be hosted on a cloud there fore there are more chances of security breach in cloud world, cloud is consists on internet computing so security is a bit concern in clouds. There are more chances of rooting more chances of DDOS attacks as compare to a dedicated server.
If kernel level is compromised security of whole cloud can be compromised.
Unknown Physical Location:
Clouds are combination of multiple servers hosted even in different geo locations, therefore physical location of software and hardware are unknown and for large enterprise site audits and inspections are difficult.
As cloud computing is internet computing therefore an organization cannot get compliance for SAS70, PCI, SOX and HIPPA
Clouds are not as flexible as a dedicated server, cloud computing is based on virtualization therefore you cannot run applications that requires dedicated server or application that uses virtualization techniques.
Enterprise requires custom modifications which are not possible in virtualized environment.
Integration with multi data center hosted applications is difficult to achieve due to virtual environment. and incompatibility of cloud applications with custom developed applications.