A watershed is where things come together into a single point. Think of a collection of streams coming down off mountains, coming together at a single body of water, like a river.
Bill Laing is Microsoft’s Corporate Vice President of the Shared Server and Cloud business. Bill has a blog post which is the start of a series telling the world about Windows “8”.
These posts coming from him are all from the watershed of Windows “8” knowledge, brought together by the single point where they all meet. These posts are information from the product teams that are making it, disseminated by the leader of those same teams.