There is one meetup group that openingly posts sledfests at Cannon and Wildcat as well as some members of the AMC NH Young Members group.
Perhaps peer pressure will help persuade them to go sled on a hiking trail and not the ski trails.
In the interest of full disclosure it is my meetup group that has posted the sledding events that Bob is referring to. We had been told by ski patrol twice at Cannon and once at Wildcat that as long as the lifts were off and the ski area was closed they had no problems with us sledding down after hiking to the summits on the hiking trails. Whether they were stating "company policy" or their own "personal beliefs" they are responsible for safety on the mountain so we figured if it was OK with them then it was OK to do.
On Cannon this year we spoke with the woman in charge of the ski patrol and she said that despite what we had been told in the past we had been mis-informed - sledding on Cannon was not allowed before, during, or after hours. She was very polite and understanding and allowed us to descend the ski trails but asked that we not plan any such events for Cannon in the future. If that is their policy we will respect that.
Same goes for Wildcat. The most recent posts in this thread introduced (at least to me) the concerns that Wildcat has regarding sledding on their mountain. If that is their stated policy, which based on some of the previous posts it sounds like it is, then we will respect that one too. We have modified the upcoming hike that had included sledding down their ski slopes.
No need for peer pressure

While I can't speak for any other groups, mine wants to play by the rules. We keep our group sizes to 12 - 15 people except in Wilderness Protection Areas that limit group sizes to ten (or fewer). Now that the rules have been stated we will follow what the USFS and the ski areas agree upon.
While I suspect the concerns from both Cannon and Wildcat stem from insurance and liability concerns (I have been a risk manager for a multi-national insurance company for the past 23 years so I understand where they are coming from) I still find it interesting that in the "Live Free or Die" State taxpayers can be restricted from using State (Cannon) and Federal (Wildcat) land while private entities use that same land to make money for themselves. That however, is a conversation for a different day