This does raise a point though. Flash if that's what they're using does have a built-in Peer to Peer system. Assuming most folks have a router with UPnP turned on or a method is implemented to allow NAT Transversal, couldn't they in theory use a P2P distribution method? I wonder wonder how that would work on a mass scale. Lots of crushed last mile networks but I believe it would help out a lot in a LAN environment so you're not taxing the CDN further. One machine gets the 720p/1080p stream and sends it out to others who do the same on the LAN.
Yeah, the only thing P2P would do in this case is destroy the upstream capabilities of any network where there are a number of SB viewers...because most last-mile networks still are lacking in the upstream capacity department (I'm talking raw capacity, not provisioned speed). Never mind the fact that many folks couldn't stream more than 480p on the upload side anyway.
In a situation like this, you want a branching topology, where the data flows in exactly one direction: toward the end user. There will be branches along the way ("repeater nodes") but anyone serving the stream should have enough upstream bandwidth to serve several users (or, you know, 1000...16GB RAM, high-cpu, 2x10G NIC machine). And, for the next ten years or so, the only place where upstream bandwidth will be reliably available in that quantity is a data center.