Why would a business want S+S?

This morning I presented at Microsoft Tech·Ed on the topic of S+S. The session went well, with some good audience interaction, and I think there were a number of people that hadn't understood the significance of S+S, until seeing it in action in the Xero world.

S+S presents some challenges for traditional developers and IT/Systems people, because it involves taking what is already familiar (being installed desktop software), and making this interact with online service. In my opinion, S+S extends the power that exists with having centralised data (on and via the web), with the mature and established applications. I also believe that rather than this be a transitional process (to bring everyone on to the web), it is a collaborative process, allowing customers to make the choices about what they want.

In particular, Xero has a developer interface that enables all types of software (Online, Desktop, Mobile & Enterprise) to securely access information instantaneously. Interestingly, one of the questions asked at my presentation was "Why would a business want this?" I believe I was able to answer it, but would like to know your thoughts.

Stuart