Delivering multicast to end users is fundamentally not hard. The
biggest issue seems to be with residential CPE (pretty much the same
problem as IPv6, really).
Well, more than that, since I don't really want my DSL pipe saturated
with TV that I'm not watching, you need some way for the CPE to tell
the ISP "send me stream N"
I suppose with some sort of spanning three thing it'd even be posssible
to do that at multuple levels, so the streams are only fed to people
who have clients for it.