There is much confusion out there around the intersection of SOA and cloud computing, something I addressed in my latest book. The Open Group's Chris Harding has also written a great article on that topic, diving into the issues around SOA and cloud computing -- in other words, about the confusion.
This issue can be best summarized by this quote: "'I just got my people trained on SOA,' I heard someone say recently, 'and now they want to go off and learn about cloud computing. When are they ever going to do some actual work?'"
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A common misconception is that cloud computing is replacing SOA, which is not at all true. The two are very different. SOA is an architectural pattern; it's something you do. Cloud computing is nothing more than a set of architectural options, including private, public, and community clouds. They go very much together; indeed, cloud computing makes SOA much easier and much more valuable.
Another quote that got my attention: "Independent analyst David Linthicum, for example, says that 'SOA is all about the process of defining an IT solution or architecture, while cloud computing is an architectural alternative. Thus, SOA can't be replaced by cloud computing. In fact, most cloud computing solutions are going to be defined through SOA.'"
(I'm not an analyst, by the way, in case you where wondering.)
The challenge here is education. Let me tell you: It's been difficult enough for those in enterprise IT to get SOA, and now cloud computing seems to be complicating things, even though it should not. However, the fundamentals of the SOA are pretty simple, and so is the place for the clouds.