Just read a great demystification of some of the main tenets of cloud computing over at Gigaom. Joe Weinman makes a great short list of the main drivers of cloud computing, and how they may or may not fit your business and computing needs.
So again, the fact that the cloud means many things, and offers both benefits and potential drawbacks for some deployment strategies proves the importance of choice when it comes to cloud computing.
On the most extreme side – it must be argued that not all software will eventually move to a cloud or SaaS model. It is just impossible. Differing needs and the environments that support those needs will stay varied.
But inside the cloud deployment model – one size or shape will certainly not fit all. Public and private clouds, with even more permutations within those concepts, will drive value and innovation.
The companies offering one flavor of cloud computing options (namely a multi-tenant monolithic lock-in based model) cannot truly offer any added benefit to an organization – and I believe as more open and flexible cloud offerings become available, these limitations will become even more transparent.