There's been much press on this lately.
We've long held that whilst there's a future in cloud computing and software-as-a-service, the current limitations in reliability and privacy mean a pure-play cloud solution is unlikely to ever be truly viable.
That's why we prefer the software+services model. Giving choice between hosted and on-premise should ensure we get the best of both worlds.
CIOs On Cloud Computing - Cloud Computing Blog - InformationWeek