Vertical video is an important issue. Please watch this public service announcement on the issue:
I wish Apple would at the very least have a warning message pop up every time someone tried to record video vertically. A message that could not be turned off and of course would never show up if you record horizontally. Maybe a PSA like you posted could also have to be played by the user before he/she can even use the camera. Not too long, maybe about 30 seconds. Apple could also disable the video recording function if it's not being held horizontally, forcing people to go into the settings to change that to "Allow vertical/portrait video recordings" or something like that. Apple needs to do something.