Yes, you're right. I agree that there are times that denormalizing makes sense. My point was that the item said:

* Throw away the normal forms you learned in school

* Denormalize [...] whenever it makes a query faster.

I think that's bad advice as stated. As you imply, you have to know why the rules are there to know when to break them intelligently. I didn't get that message from the item as posted, rather that the author thought that NF had little value, which probably doesn't belong in a list of database tips and tricks.

[edit: format]