The Microsoft Corporate Strategy Group has just released a new whitepaper, "The Economics of the Cloud", which details underlying the economics driving IT's shift towards the cloud.  This paper, written by Rolf Harms, director of the Corporate Strategy Group and Michael Yamartino, manager of the Corporate Strategy Group at Microsoft, provides great guidance to IT leaders as they consider their investments in infrastructure, architecture and skills during this shift.  You can read more about the paper here