What is the Service Level of Agreement (SLA) for the security of the various Cloud Storage Services like Amazon, Google, Azure, Sales Force Automation and so forth?  A paper titled:

Enabling Security in Cloud Storage SLAs with CloudProof

Paper: http://research.microsoft.com/en-us/um/people/helenw/papers/cloudproof-longer.pdf

This paper maintains that security is a way to differentiate the cloud systems.  The cloud system that can demonstrate security levels will certainly differentiate the Cloud product.  The paper further describes the difference between cloud security and the secure file system.

There is a lot of stuff to review in this paper!  Check it out.