Robert,
This goes beyond the scenario you explained. Let's say I have a business supplied laptop running Windows 8 Pro which is joined to our work domain. We use Office 365 as our e-mail service along with the Office suite. This ID is what Microsoft calls an "Organizational Account". I log onto this computer and now I want to connect to the Windows Store to download some app. Unfortunately I would now need to create a new Windows ID which is labeled a "Microsoft Account". Both of these services are Microsoft products on different platforms but the intended use of both accounts are business.
Microsoft has no way for a business user to log onto the Windows Store with the Organizational account.
What this now requires is yet another sign up process which cannot be controlled by the organization/business. It effectively forces a user to link a personal account (such as Outlook/Hotmail).
Wouldn't it be more intelligent to permit a federated account across platforms so IT Departments can control the downloading of apps on a business computer?
If a company stops using O365, I'm sure there can still be some federation between AD and the Windows Store.
In your example of a person getting fired, as you would expect that user would no longer have access to those apps or account nor should that user have access. That's exactly the point. Without this ability to synchronize accounts, control is given to the user as they user is now forced to manually sign up for a Microsoft Account (outside of the company's control). If this user was dumb enough to use his corporate account for personal use, the user SHOULD lose access to all of that data.