Jeff Schneider has a funny piece that puts SOA in an historical context.
Although the "famous brand of plastic building blocks" analogy is not new, it is very important. I get asked a lot why we need specifications such as the Service Component Architecture. "Why do we need another invocation mechanism?" The answer is that SCA isn't just an invocation mechanism. Rather, one of its key features is the ability to regard logical chunks in our infrastructure and applications as reusable building blocks. Blocks that both provide and consume other services. Jeff's piece illustrates that quite nicely.