There is lots to wrap your head around in this article. Since we've decided not to pass judgment on right and wrong in this thread I have to say that I'm wanting to see if I can replicate what they did. Not for malicious reasons but to better understand the intentionally secretive ranking methods @Google. I'm not going to because Google has very specific guidelines against it, but wow.
I've always felt that duplicate is wrong, wrong, wrong and that using it was poison but Google didn't have Rands back on this one, it leaves a mere mortal webmaster feeling quite vulnerable.