Yeah, long virtually guarantees crappy, but short can mean so coarse that intent isn't clear - LEO and courts pick up the pieces. Big item not covered here is

Yeah, long virtually guarantees crappy, but short can mean so coarse that intent isn't clear - LEO and courts pick up the pieces. Big item not covered here is practical enforceability. Ingress filtering to prevent IP packet spoofing is much easier because there are many valid uses for CID spoofing. Can't configure a session border controller to filter "deceiving or defrauding spoofed caller ID values."