What few things need to be the same so that everything else can be different?

This question, poised by Michael Tiemann, CTO of Redhat, is at the heart of many of the decisions facing IT today. This question defines the power of web services as well as the move toward managed desktops in corporations. Finding the balance in this question is a critical decision facing technologists as they develop enterprise architectures and operating models so that IT can serve the business.