Recently I attended a cloud interoperability forum organized by Stephen O'Grady and Dave Berlind (thanks to both of them for corralling such disparate voices). There I got into a mini-argument with Tim Bray, who was asserting that the most important thing from an interoperability perspective is substitutability, i.e. there should be no vendor (cloud provider) lockin. That CIO's say, if there is lockin, they are not moving stuff to the cloud.
My argument against it is simple: there are many dimensions to why an organization may choose to move some of its workloads to the cloud. Substitutability or no vendor locking (see my blog) is just one of them, and I would assert not even the most important one for now. Cloud economics, security, loss of control, network effects, bandwidth, ecosystem, integration needs etc etc all important. Every CIO is being asked to do more with less, and consequently, substitutability or lack thereof is just one of the dimensions to the complex puzzle of moving stuff to the cloud.