The point of SOA, that the Telecoms (IMHO) seem to be grasping as a lifeline, is that SOA enabled systems allow you to take legacy and entrenched technologies, and present them as an consistent, controlled API that lets your business users develop new and previously un-thought-of ideas without needing to re-architect everything in the company.
By having a unified language (WSDL) as your interface, you can prepare your technology silos for interoperating. By implementing SOA now, instead of doing direct-to-data-source, you automatically make your data sources consumable by parties and business needs you've never considered.
WSDL is finally Corba-that-works.
