Vinoski and Tim are right about Contract first.  I would expect no less from one of the Fathers of distributed computing.  I learned this lesson first hand over eight years ago working with Charles White and Eva Guo on a project at HP.  Yes, we built service-oriented systems back then too!

Don Box is giving a talk on Metadata Soup: Contracts, Models, and Types on the Connected Systems Infrastructure Track at Tech Ed this year.  There is no doubt in my mind that he will turn this topic upside down

Aaron has been blogging a lot about contract first and proposed a birds of a feather session.  Vote for it and attend.

(Clearly I'm at that point where my to do list is too long so I am procrastinating and catching up on the blog roll.)