The hyperbole to reality ratio that surrounds cloud computing is higher than anything I have seen since ATM. If you remember ATM, industry pundits told us that ATM would be our next and last networking technology. It wasn't.
One of the big differences, however, between cloud computing and ATM is that there were well agreed to specifications that defined ATM; e.g., constant bit rate, variable bit rate, etc.. Unfortunately, there is relatively little agreement in the industry, particularly on the part of IT organizations, as to what is meant by cloud computing.
I have been involved in a number of benchmarking projects. As such, I realize that the results can sometimes lack precision. However, a factor of forty in terms of cost savings is indeed compelling. It says to me that there is something here that is important for IT organizations to understand and apply judiciously in their organization. We just have to cut through the myriad layers of hype to find exactly what the reality is.