When administering AGOL it would be very useful to have a function in the 'My Organisation' section which allows the adminstrator to download a CSV (or similar) of all the current usernames and corresponding email addresses.
This idea has been merged with Export list of ArcGIS Online Users to Excel.
As an administrator I currently keep a separate spreadsheet containing the details of all my users. However as the number of users grows it is becoming more difficult to maintain. If I were able to click a download button which gave me a CSV I can then import this into Microsoft Outlook in order to create a mailing list.