Michael;
an option with customers. There isn't a demand, so the providers don't put the resources into it...
That is the way our economy works...
The economy around best effort multicast is as follows ISPs want to get more money for additional service of multicast receivers pay nothing to receive the same service as unicast with the additional complexity senders are forced to support unicast service to attract enough number of receivers, even if they pay more for faster connection The story may be different for closed groups of senders and receivers but they are negligible. And, if receivers start using resource reserved communication at their own expense, they are motivated to use multicast to reduce communication cost. But, it will take time. Note that BGP is incapable of handling such situation. Masataka Ohta