The "Windows monopoly+Office monopoly=Microsoft" story was absolutely true 10 years ago, but less so now.
1. It looks as if the "Office" revenue figures are coming from MSFT's reported revenues in the Business segment. That's not all Office. Based on what they've said at the last few Financial Analyst Meetings, Exchange is approaching $2B/year, SharePoint is about $1B/year, and Dynamics (formerly Microsoft Business Solutions) is more than $1B per year. I also know that Project has been a $1B/year business for a long time (believe it or not), and products such as Comms Server and Visio contribute around $500m/year. Margins on all these products are lower than on Office, but most (not Comms Server) are profitable.
2. In addition to all the non-Office products that compose its Business segment as mentioned above, the Server and Tools business (Windows Server, SQL Server) is profitable (30% margins) and growing revenues average of 15% for the last six years. Not monopoly, but a good business.
Look at all these stats together, and seems like they should get out of search and advertising and sell off (or scale back to maintenance mode) most of the consumer online sites, focusing instead on hosted business apps--they're already doing it with Exchange and SharePoint, why not Office? If somebody's going to canniblize their "real" business, it might as well be them.