cloud computing

If SaaS, PaaS, IaaS is to benefit a company, the scale of economy has to take into play. For a large enterprise, for example, WalMart, it's IT infrastructure is so huge and so big, it just make sense to have its own private cloud. It is not imaginable for a company as big as GE to outsource it's infrastructure to Google.

The shared services will provide scale of economy by its own IT.

If google or others hosting this for them, it might just cost too much for the service.

Private cloud for small and medium business may not make much sense, they can use Google for scale of economy. But as the company grow, the steady flow of cash toward google might have to be stopped.