Real Media and M-Bone feeds

And wouldn't a cache box with multiple people watching "live content"
basically bring us right back to multicasting? One stream to the cache
operator, multiple streams out to the clients... Multicasting.

There's a subtle but very important difference: such "multicasting"
does not involve injection of customer-originated routing information
into the global routing system.

Which means that scalability is not an issue.

There's at least one commercial service that does this with RV and