What you suggest is absolutely unnecessary. Merely requiring an identifiable contact is enough to prevent this sort of behavior -- and this was how things were

What you suggest is absolutely unnecessary. Merely requiring an identifiable contact is enough to prevent this sort of behavior -- and this was how things were before voip opened things up to untraceable abuse. The phone company doesn't need to police anything -- they just need to identify the endpoints of a call when a subpoena is issued.