·Verizon Online DSL
That's why you don't deliver video as a unicast stream from anywhere near the Internet's core. That's not the way Akamai does it, that's for sure. Put nodes as deep as possible into ISP networks (as deep as, if not deeper than, Akamai's current nodes/Netflix OpenConnect), then push the stream to them (total bandwidth used: ~20 Mbps per node). Then anycast (or use DNS based resolution, whatever floats your boat) over the last 50-250 miles, depending on how far you are away from an ISP core router.
Oh, and serve everything over UDP, with no ability to fast forward/rewind the stream other than what the client can handle on its own. What you want is a network of dumb pipes piping a data firehose to wherever it needs to go...the smartest piece of the puzzle should be bandwidth detection (serving 360p, 480p, 720p or 1080p), and that should be client-side.
Oh, and don't forget the dual 10 Gbit NICs on the edge nodes. So you can serve 1000 viewers from one system.
Is the scale of this event enormous? Absolutely. Is it a special case that, if handled correctly, requires significantly less hardware per streamer than you'd normally expect? Yep.