Think about it; its not that farfetched. In Outlook 2010 Microsoft provides you with the Social Connector. This is a bar that appears at the bottom of the email window when you open a message and allows you to link social networking information with your email. The Social Connector lets you do most of the things you already do by going directly to your social networking websites; share status info, pictures, files, and, obviously, email.
Implementing SharePoint based social networking in your datacenter would certainly increase the workload on the datacenter, but if you are already supporting a major SharePoint rollout, you should have planned for the appropriate increase in network traffic associated with the social aspects of collaborative computing.
The concept of unified messaging is not a new one in the business world, but it is not something the average end-user is likely aware of. But tell them that that they will only need to open a single application to access all of their social networking and email and you might grab their attention, especially if that application is one that already has a couple of hundred million users already (that number is based on an approximation of the number of Exchange mailboxes currently in use worldwide).
Even users not on a corporate Exchange server have a good chance of having a copy of Microsoft Office on their computer, and considering Microsofts aggressive push with Office 2010, its likely that Outlook 2010 will find itself on the vast majority of new computers sold over the next few years. Now think about this; Microsoft has the potential to become the face of social networking regardless of who decides to provide the social network backend.
And after a few years, when people get used to having that single point of contact for all of their social networking and communications needs Microsoft can roll out a worldwide social networking backend that will offer an easy one click style migration of all of the data currently being aggregated by the Outlook client and have an instant presence as the backend provider of social networking services.
People in the technical community like to scream and yell about the evils of Microsoft and take shots at the quality of the software, and lots of other very technically focused attacks. But do you think that the average social networking user cares about any of that? And if Microsoft is able to offer a secure social networking environment, with good privacy controls, and the flexibility to deliver what the user (and developers) need, then it is very like that a decade from now people will be looking at case studies of how Microsoft made the transition to a dominant cloud application provider.