There is a lot going on in the cloud computing space, and SOA is clearly along for the ride. Indeed, there are many things that cloud computing providers (and that's a rather big category these days) and those building SOAs can learn from each other. I'm just scratching the surface here.

What SOA can learn from cloud computing:

Service Design
Those who deploy services in the cloud, such as Amazon, TheWebService, Force.com, have done a pretty good job with service design. You really have to do a good job in order to rent the darn things out. Many SOA projects have a tendency to build services that are too course-grained, too fine-grained, or just not at all well designed.

The reality is that services that are not well defined and designed won't sell well when delivered on-demand, and thus those who provide services out of the cloud - which are most major cloud computing providers - have to spend a lot of time on the design of the services, including usability and durability. I urge those who build services within their SOA, no matter the enabling technology and standards involved, look at what's out there for rent as good examples of how services should be designed, developed, and deployed.

Service Expandability
Cloud computing services are designed to expand as needed, and those leveraging cloud services do so because they can get the services on demand, when they need them. The ability to expand services within a SOA is typically a painful and expensive process.

The fact of the matter is that services designed and developed within enterprises typically are not designed to scale. Indeed, the core issues with SOA revolve around the fact that many don't focus on scaling until it's too late and difficult to fix. Cloud computing providers had to figure out scaling rather quickly.

What cloud computing can learn from SOA:

Service Governance
There is little notion of governance today within cloud computing, and thus there is little control and implementation of policies. Therefore, many enterprises are not diving right into cloud computing.

Governance, while not always well-implemented, is a fundamental fact of life with SOA. The ability to set policies around services and the ability to manage changes to those services is a critical success factor. Indeed, as we weave cloud computing-delivered services into applications and within our SOA, you'll find that many things break as those services delivered on-demand change over time. SOA typically can manage those changes through SOA governance systems, but perhaps some of that governance should come from the services that come out of the clouds.

Driving from the Architecture
If you're doing SOA properly, you're driving it from the architecture to the technology. Within the world of cloud computing, the resources on demand are really the starting point. With cloud computing, the need for a well-thought-out architecture does not go out the window; indeed, it's even more important, considering that you're extending the architecture out of the firewall.

Using cloud computing resources is really more about reaching your architecture out of the enterprise to incorporate cloud resources, and thus it's important to remember that your architecture does not end at the firewall. Indeed, the need to understand both the resources that exist within the enterprises, and the resources that are cloud-delivered, is even more critical, as is the need to configure these resources correctly in the context of an architecture, and to meet the needs of the business.

Clearly, SOA and cloud computing go hand-in-hand. Cloud computing is just the ability to leverage new platforms and resources that you don't happen to own. Nothing really changes outside of that, including the need to do SOA right. However, cloud computing is accelerating the adoption of SOA by providing aspects of SOA on-demand. SOA can learn a lot from the clouds, and the clouds can learn a lot from SOA. I'm happy to make the introductions.