My guess is that MS wants to develop it's own web-application stack-- XAML etc. on Vista clients; MS-designed SOAP protocols; .NET apps running on Windows servers.
Google and friends are getting there first because they're using already-deployed technology: HTML, Flash, Javascript in any browser on the client; HTTP requests to get data; whatever kind of apps you want (Java, C, C++, Perl, Python, Ruby) running on Linux servers.