I suppose you're free to challenge Nokia on the basis of your theory that their usage is purely decorative. I suppose though we could expand the notion of fair use to anything where starting an action would make the plaintiff look silly. :-P
That would fall under de minimis, not fair use. And, in this case, the violation probably is de minimis, that doesn't stop it being a violation, it just means it's not worth the court's time. But, as I've said before, this isn't really a discussion about a Nokia box, it's about the principles behind it.