Yes, and with significant outages too. Again, I'm not saying multicast doesn't work. Multicast works well as long as you can guarantee that your network topolog

Yes, and with significant outages too. Again, I'm not saying multicast doesn't work. Multicast works well as long as you can guarantee that your network topology, components (switches and routers), servers and usage pattern will be predictable (and you test everything rigorously before going live). I can imagine that being true at some places with extremely tight focussed requirements. In a dynamic environment where you'd be scaling continuously and adding components and servers and building new services, this becomes a non-starter. Multicast implementations doesn't fail gracefully -- there's very little warning before things come to a complete halt and need complete shutdown and reboot of entire network.