Cloud Computing for Medical Record

How will cloud computing accommodate confidentiality and permissions to use the data for data mining?
Assuming it can, the thing most needed is a linked database containing a complete and continuously updated list of every disease and syndrome known to man. Thus any provisional diagnosis or problem could in real time list every related entity (differential diagnosis) meeting the same of similar basic criteria. The inaccuracy of initial diagnosis remains an ongoing problem in US medicine, 15-17% missed or wrong diagnosis by current studies. A statistically derived differential diagnosis would go a long way towards inducing the clinician to look for possible error or deeper consideration.