How is this different with an RIA vs non-RIA web app? You mean like something in Flash or Flex vs HTML? Not sure I get what you mean.
Are you saying it's more work for a localized app (coolapp.com/customer1/) to interact with services.coolapp.com than with coolapp.com/customer1/services. And does the latter imply that there would be massive redundancy or can one go about routing queries to avoid that?