Just noticed today, right now (22OCT2013), that the WindowsAzure portal now filters the view based on Azure Active Directory. Have a look at the graphic below and you will understand what I am talking about-
If you were to login today to the portal, you will see the following message come up- “The subscriptions view has been restructured to filter by directory. Resources shown here belong to subscriptions associated with the ‘Default Directory’ directory only.” And you cannot view details for all directories at once.
What does this mean?
Basically this means that when a subscription is created for a user, a Microsoft Azure directory (<<your Microsoft account alias>>.onmicrosoft.com) is created and the current Microsoft account (user) becomes a part of that directory. And now you add co-admins as part of this directory. Essentially a directory container is added to the azure subscription.
Essentially, think about the number of Azure AD tenants being provisioned today? Phew! Far too many. And are the users are getting authenticated against Azure AD/ACS? Yes.