Just wanted to drop in to talk about the act of defending your trademark. It’s not that you have to defend your trade mark per se, but that you have to make sure your trade mark doesn’t become generic.
For example, Xerox. It’s common to say “Xerox this exam paper” even when the copier you’re using is a Canon, or Brother, or whatever. If it gets to the point where your trade mark loses its ability to connote origin (the functional essence of a trade mark, literally a “Trade” “Mark”), then it’s generic, its useless. Wiki has a nice list of generic trade marks: Escalator, Kerosene, Thermos, Yo-Yo. http://en.wikipedia.org/wiki/Generic_trademark
In this case, Nutella is still being used to refer to Nutella spreads, so it’s not a case of genericising the trade mark. It’s barely infringement in the traditional sense - you’re using Nutella to refer to Nutella, what’s wrong about that? What’s wrong, however, is that the website’s use of the trade mark “Nutella” can be taken to be connoting some kind of connection, whether it’s sponsorship, approval, etc. That may give rise to a claim (I can’t say, for example, I’m a Disney day care without implying that I’m somehow connected to Disney, even if I’m not selling fake Disney stuff).
On a non-legal review, you don’t want nutballs speaking for your product. Trademark has kind of evolved past the literal “Trade” “Mark” now, it’s the face of your product. I buy a drink labeled “Coke” not because the label tells me it’s from the Coca Cola company and therefore I know that the product is safe and tasty, I buy it because “Coke” now has a funky image and it’s cool, and so on. It’s the reason why Pepsi wanted MJ to be seen holding that Pepsi.
Imagine if you had Hitler holding your product, and being associated with your trade mark. Sure, people still knows that the product is the same, and it comes from you, but it now “feels icky”. For a real like example, see Burberry and the Burberry Chavs, where hooligans ruined the brand image of a luxury trade mark (the Burberry tartan).