Sometime in the future we'll look back and wonder how our televisions and movie screens became vertical. This post will go into the evidence basket.
I lol'd, I'm reading this on a vertical monitor right now. My secondary monitor is vertical due to cramped desk space, so I can have my horizontal monitor still centered when I look straight ahead.
Developers are a bit different in this regard. I used to use a vertical monitor in 2007 because, well, it's pretty great for big chunks of code and web development in general.
As good as it was, I never wanted to watch videos in that way.