It’s been about three years since Amazon made its risky bet on delivering computing and storage via the cloud. It started by offering commitment-free, pay-as-you-go storage, enabling startups to start scaling their businesses without significant investment in capital equipment. It later added compute cycles to its services and today has a host of other offerings,including a content delivery network.

Both the hype and perceived value around cloud computing has expanded since that first shot was fired, but enterprises remain cautious. What’s becoming clear is that the best way to get them to join the cloud revolution is to introduce private or internal clouds for corporate IT and then gradually merge or offload data from those private corporate clouds into public ones. In other words, for cloud vendors, the big opportunities in the cloud space are in helping enterprise customers deploy their own internal clouds (like Elastra or the larger vendors do), helping them manage multiple clouds, and figuring out how to transfer data between internal and external clouds.

Earlier this week Imoderated a panel at the South by Southwest Interactive festivalin Austin, Texas, that included Werner Vogels, CTO of Amazon’s Web Services. He said some of his enterprise clients are using the cloud for testing and developing software and some forhigh-performance computing, such as Eli Lilly. But many, he acknowledged, still need convincing.

Yousef Khalidi, a distinguished engineer at Microsoft helping to build the software giant’s Azure cloud platform, had a cautious assessment of how enterprises are likely to view the cloud: He thinks corporate IT will want to keep its cloud under corporate control, and that as a result the creation of hybrid clouds — or “cloudbursting” — where certain jobs move from the internal servers to an external cloud, are going to be a preferred model.