When Mette-Marit married Haakon, there was talk about getting her a more regal sounding name in one editorial or something like that.
The interesting part is that when Haakon's grandmother - Crown Princess Märtha married Crown Prince Olav - there were talk about giving her a more Norwegian-sounding name and, I can't remember which, at the moment, but either Mette or Marit were one of the names suggested. It should be noted that Märtha was Swedish and married Olav less than three decades after the union between Norway and Sweden was dissolved, thus feelings in Norway might've been suspected of being a bit tense towards Swedes...
I'm personally just thrilled that Sonja's spelling her name the way she is, and not an alternate Norwegian spelling - which is actually discouraged now, but there are people who spell their name that way - Sånnja. It's the way it is pronounced, yes, but it looks awful in writing, and not very regal.
I guess it is important with the recent influx in commoner brides - to consider what you name your child
You never know where they'll be in the future.