Is it possible to auto tag pages and documents based on a users active directory data, such as the team, section, department they work in?
You can create few content types inheriting OOB content types (Item, document, ... ) with necessary fields (like team, section, dept), and use this as your base content type to create lists, documents libraries. You can then create an event receiver for these content types, that update the columns based on the loggedin user.
To use a Event Receiver is probably the right way.
Here is a link about Event Receivers http://msdn.microsoft.com/en-us/library/ms437502.aspx
You probably need to implement the ItemAdded and the ItemUpdated Event.