I think I finally get what it means to design a Service Oriented Architecture.  In normal coding practices the designer is always thinking in terms of the bigger picture, always worried about how their piece of code will work and what they may need to tweak to make it work in this particular instance.  In a Service Oriented world the worry now is in how will my service perform, period.

Whenever we write a function for a class or a piece of code we always write the function for that class or for that purpose.  So in essence when we write something for a Service we are writing it just for that service and nothing else.  A true Service thinks only about itself and how best to encapsulate its own functionality into something useful, later we can decide how we want to implement this service.  But the Service does not change.  You can extend its functionality, but if you plan your service correctly in the first place perhaps you should write a new service, but do not write it for the other service.