I think you fail to understand exactly what people are 'spazzing' about. They included that footer to try and prevent exactly what Null did- publicizing that they are trying to identify and investigate internet users from a forum. That makes everyone else the 'unintended recipient.' They don't want anyone to be able to reveal to the world what they say in an email; they are purposefully trying to chill free speech. They are not alone; those legal footers are used by many people, even lawyers, when they send ridiculous demand letters or 'requests' because they know there would be public backlash if they were discovered. Otherwise they could only include it when sending particular information; that said, if you don't want information revealed, you don't send it in an email to someone unless they agree beforehand to not share it. And you check that you're sending it to the right place.
I know that such notices have weight in the US- if you send someone something, you generally cannot control what they do with it (with the exception of national security letters as referenced earlier and possibly 'revenge porn'- a thorny issue that will eventually have to get sorted in court, I think). But I don't know if actual kiwi citizens have to kowtow to such general notices. I doubt it; I suspect the statute applies to physical goods and some bright mind decided to try and use it as a scare tactic because people wet their pants when they see statutes mentioned.
