I was recently working with a client who had developed a solid demonstration vehicle showing many moving parts. As I was working with them, we identified that the service interfaces were developed with varying degrees of granularity. The data granularity for some of the interfaces was fine grained expecting small sets of data whereas other expected a full document or were coarse grained.
To simplify the demonstration and complete the round-tripping exercise they were shooting for, we standardized the WSDL definitions to use the same Schema and to push the entire document across the wire between the services. In essence we standardized on a coarse definition. This then untethered the controller service they had defined in BPEL to just copy the top level element between services.
As changes occurred in the demo, the refactoring demonstrated that maintenance or updates were much simpler or non-existent.
From a business perspective using the business documents in the interfaces provides a SOA centric approach towards development. This approach doesn't always make sense as with very large documents, there may technology or complexity reasons to limit the use of such an approach. In those cases fine grained access make sense albeit with more work on the orchestration side.