He didn't quit Google+ he just changed his privacy settings so that you can't track how many friends/followers he has. You can still see his profile right here: https://plus.google.com/u/0/104560124403688998123

You're wrong. Currently when a flight enters an Air Traffic Controllers sector, a piece of paper is printed out with details of that flight on it, these are called 'Flight Progress Strips'. Controllers use these strips to keep track of where a flight is supposed to be going and what instructions have been given to it. Basically EFD aims to replace these paper strips with an electronic version.

They don't write the fliight number on a piece of paper. When a flight is due to enter a controllers sector, a strip will be printed and given to the controller. This strip will have all the details for the flight including callsign/route/destination etc... When a controller gives instructions to that flight, he writes on the piece of paper so he can keep track of what instructions have been given to it.

How do you know?

As everyone is.