Conventional service-oriented architectures (SOAs) have been found to have:
These problems are especially acute at scale.
Frank Cohen recently posted a paper on IBM’s developerWorks, "FastSOA: Accelerate SOA with XML, XQuery, and native XML database technology: The role of a mid-tier SOA cache architecture," that presents some interesting alternatives to this conundrum.
The specific FastSOA proposal may or may not be your preferred solution if you are working with complex SOA environments at scale. But the general overview of conventional SOA constraints (in the SOAP framework) is very helpful and highly recommended.