Agreed that if doing TCP, you either need to limit the PoPs, or be doing it with a an app that is highly resilient and capable of dealing with unexpected loss o

Agreed that if doing TCP, you either need to limit the PoPs, or be doing it with a an app that is highly resilient and capable of dealing with unexpected loss of a session and reconnections. The same is true of UDP. For stateless short burst things like DNS and NTP it's not a big deal, but it is for video conferencing and other stateful protocols built on top of UDP. It's not a layer 4 issue as much as an application issue. As to the second point, ARIN could not possibly require 25% utilization. That's 3*10^23 addresses on a /48. Or if they're counting utilization as the number of subnets, that 16,384 /64 networks. Look at some sample companies, Valve has a /44 from ARIN. They're only even announcing 6 /48 prefixes right now. Netflix has a /32, they're announcing less than 20 /48 prefixes. I worked at a small MSP who provides ISP services to less than 50 clients, and they were allocated a /32 years ago and have yet to announce a single prefix. Burning a /48 for an anycast network is not a big deal, and getting another /48 is trivial. Getting a /24 for an IPv4 anycast network is much harder. So yes, for IPv4 anycast to take off we need the ability to advertise longer prefixes, but /48's are abundant enough that one can be sacrificed.