When a LP video is just footage from the game and thats it, I can understand Nintendo putting a stop to making money off of their product.
But if someone does a LP and does commentary or reviews and go to a lot of work editing and showing us tricks, secrets etc. then I think Nintendo should leave them alone.
But the problem is if Nintendo puts their adds on all LP videos then odds are they wont pick and choose and the entertaining videos where they have game footage and other edits or commentates will get punished too.
So in the end I think Nintendo should leave it alone and look at it as free publicity.