The way I read it Billy G. just liked the idea so that his secret emails about crushing any competition couldn't be fowarded to the police. Or he could just wrangle the law untill the mails were unreadable.
Interestingly, Lotus Notes already has an option to prevent forwarding and expire email after a certain date (I've never tried the "expire" thing so I'm not sure how it works - however I suspect it is advisory rather than trashing the email after that date). As you rightly point out, the forwarding can be resolved by copy & paste (I think printing is blocked, presumably they could block copy&paste as well although it is still active), and "reply with history" still works IIRC - after which you can change the address you are sending to. It is more to suggest to the recipiant that they shouldn't be forwarding the message around, rather than to stop them - there is always a way around something, and a screengrab cannot be stopped :-)
Plus I haven't seen the world collapse through the introduction of this feature, although M$ are likely to implement it in the most annoying way possible.
Chris
