> how about http://some.storage.service.tld/path/to/video.mkv or even rtmp://some.streaming.service.tld/path/to/stream ?

Well, if I click on the first link, a video doesn't play (that would be the case even if the link were to an actual MKV video). The second URL isn't even a hyperlink on news.ycombinator.com. But if I click on a valid YouTube link, a video plays nearly immediately.