The reason almost all video and film screens (as well as embedded players) are wider than tall is because our eyes are horizontally opposed. That is not going to change any time soon.
So if you are shooting a video that will only be played on a phone, or that will be played in some specially designed display, like a specially embedded player in a web page, or a special vertically hung screen in an art installation, go right ahead and film vertically. But otherwise you should be filming in landscape mode.
</feeding the troll>