Nektar, great question.  You're right, there's huge potential for the online MS sites to be exposed as web services.  There have been a few good examples of MS web services:

  • If I'm not mistaken mappoint has been a web service since 2002 (and I believe the first live MS service)
  • MSDN introduced a WS-Security based service last year to track users
  • SQL Server stored procs have been exposed as web services since SQLXML3 came out in 2002, and SQL Server Yukon is building more support into the database engine
  • Passport implements WS-Federation
  • InfoPath supports using web services as a data source for its forms (in fact DBox and others have created InfoPath forms as front-ends for their blogs)
  • All BlogX-based blogging engines (dasBlog, .Text, etc) use web services (as does my blog, www.gazitt.com/ohmblog) 

All that said I think there's alot more potential out there, and I know of many efforts inside of Microsoft that are based on the WS-* architecture.  Many of the examples you mention above are being discussed or in development.  Expect to see alot more stuff get exposed as WS over the next couple of years...