Hacker News Reader

Is this not the sort of thing IP multicast is for?

IP multicast is turned off on the Internet.

Depends on which bit of the Internet - the BBC transmits (or at leat used to) live streams via Multicast to a number of UK ISPs.

Thank god... imagine the incredible noise

What do you mean? The whole point of multicast is that you don't have noise. You choose exactly what you want to get.