Charles Babcock of Information Week published an interesting article suggesting that Microsoft will have to at least to some degree take Windows open source if they want to stay in business. He suggests that the money to be made from the things MS builds on top of Windows (Office, Server, SQL Server, Exchange, Sharepoint, etc) is so much greater than what can be made from Windows itself that MS will have to give up the revenue stream from Windows in order to maintain these other, more valuable, revenue streams.