Back in the day I think Acorn's Econet network, often used in school classrooms, had a feature called the Broadcast Loader. When several computers requested the same file from the server, as often happens at the start of a lesson, it would notice and broadcast the file on the network for them all to receive simultaneously.
At first glance this looked like a similar thing, but on reading the article there isn't mention of IP multicasting or another way to avoid sending the same packet to several different recipients. Instead, it looks like a kind of distributed http cache or Bittorent. The load on the publishing server may be reduced, but global network traffic is just the same or greater. Surely the missing piece of the puzzle is a way for the response to be multicast to all those requesting it.
Streaming video seems like a bad example application since it is quite unsuited to the send-request-get-response model. The video stream is continuous; you don't request a frame at a time. And it is real-time, so you want as much predictibility as possibly in the route between you and the server so that the latency can be low and consistent. On the other hand, here we are talking about a Youtube-style recorded clip, which can be treated as a single file to download and then play.