Great question! I think cloud computing is really an enabler for SOA. After all, SOA is about building reusable services that can be deployed within a distributed fashion, and a cloud represents a great choice for doing that. In my book, I describe how Apache Synapse can be used as a service mediator to really provide endpoint transparency as to where the service actually resides. In other words, using something like WS-Addressing, the client can send a service request, which Synapse fields and then forwards to the actual endpoint location where the service resides, which could be anywhere in the cloud.
I'm a huge fan (and user for many years) of the cloud work being done by Amazon, and have been playing recently with the interesting work being done on the Eucalyptus project (
http://www.eucalyptus.com/), which provides the ability for private clouds following the same API-style interface that Amazon uses.
