Definitely this. I've seen multiple people say they had a cabin reserved, only to show up and find someone else in the cabin. Luckily for us, we managed to get the Blueberry 1 cabin without a double booking, but I think the double booking is more common for Honka House.
Or have your group in the Honka by yourselves, only to have someone who works there invite people who were camping to come party without your permission.