Compare between different formal Cloud definition? Based on stale and standards? (include the NIST definitions)

Hint: SP 800-145 September 2011  The NIST Definition of Cloud Computing

write briefly on Cloud Computing Recommendations suggested by NIST .

Hint:  SP 800-146 May 2012  Cloud Computing Synopsis and Recommendations

What are the Key Security and Privacy Issues?

Hints:  SP 800-144 December 2011  Guidelines on Security and Privacy in Public Cloud Computing