Alert that can't be skipped? Un-ignorable hectoring about whatever they want you thinking about today, perhaps for political ends. Makes it even easier to turn warnings into mandates, and it's already too easy. Over-application, so everybody gets told to worry when actually it should have been more targeted. Mistakes, causing needless fear. The risk of triggering largescale panic... or creeping up the use from "only dire emergency" to "often enough that people learn to ignore it". Potential for it to be subverted to malicious ends by third parties.
What are the good uses of a nationwide, rather than local and targeted, alert?
What are the good uses of a nationwide, rather than local and targeted, alert?