Microsoft already published a number of papers on security privacy and compliancy in relation to online services and cloud computing. The following paper creates a good overview of all different aspects in using ‘the cloud’ in a secure way :
A high-level discussion of the fundamental challenges and benefits of cloud computing security, plus some of the questions that cloud service providers and organisations using cloud services need to consider when evaluating a new move, or expansion of existing services, to the cloud. This document presumes that the reader is familiar with the core concepts of cloud computing and basic principles of cloud security. It is not the goal of this paper to provide all the answers to the questions of security in the cloud or to provide an exhaustive framework for cloud security.
Source : Microsoft.com