I'm not aware of any seriously bad science from Michael Mann. If you're referring to his original hockey stick graph it has been substantially borne out by any number subsequent studies using different data sets.

Certainly they need to advertise any applicable data charges or limits. But why would you want a burst line instead of a data limit? I don't see the advantage, at least not for normal usage patterns. What most people want is full speed when they are using the internet, without being charged for full speed 24/7.

Theoretically I suppose if you were sent unsolicited packets this would run up your meter, but AFAIK this has never become a problem in New Zealand.

Of course, most people don't want to risk being faced with an unexpectedly large bill, which is why most ISPs in New Zealand offer capped plans: instead of paying extra when you hit your limit, your bandwidth gets cut down.