So much hype for consumer.. Very real security risk for Business & Governments.
Good points by Tarak, our thinking is aligned on this one. I'll substitute "downsides" with "risks" because some of these may be viewed as half empty / half full arguments, but I see the biggest current risks as:
1. Market confusion. As Peter mentioned, it is a mad dash to the cloud right now. And since nobody wants to feel left out, just about every company in the B2B tech space has re-branded itself as a cloud computing company. I've heard this referred to as "cloudwashing," and the result is that companies will find it more difficult to find services specific to their needs, because of the tendency of providers to water down messaging into cloud buzzwords and ignore basic positioning and value statements.
2. Cloud sprawl. With the rapid proliferation of cloud services, IT is struggling to adapt corporate service delivery strategies. The results that we have seen have included duplication and overlap of processes and functions due to services being provisioned directly by business units; loss of control of the billing for services because no single entity within the company is responsible for the procurement and management of them; and the equivalent of "shelfware," a situation where cloud services are orphaned after the champion leaves the company or the business shifts focus.
3. Lack of cohesive integration strategy. There is no doubt in my mind that the cloud model of service delivery is the one that we will adopt for at least the next 10-15 years of technology cycles, but until the integration of all of the pieces is thought through, the sum of the parts will never add up. My company has standardized our core service offerings around the Force.com platform from salesforce.com to provide the "glue" that holds all of the pieces together, and we "mash up" other cloud services into composite enterprise business systems through API integration, business process orchestration, and data integration using services such as Boomi. But if companies just provision cloud services for siloed requirements up and down the cloud stack (from infrastructure to SaaS), the disaggregation of these services will prove to be a value destroyer.