Perhaps at the place where you fly it is safe to do so, but that would be a rare exception. The main difference of having pilots walk into the flight area is that they are aware of the risk and most clubs have a rule about announcing before entering, and should adopt one if they don't. You also know where they are coming from. At a park, people could come from any direction and may not understand the hazards. I don't insist that the new guys don't fly in parks, I only request that they fly planes that are appropriate for the location. Whether they chose to join AMA is a personal choice. I merely jumped in to say that the $200 excuse didn't wash. A new pilot is the worst person to judge what is or isn't safe. They may not even know how much space they need to land, much less determine a safe distance for others that may be around. Add the injury potential of a 40 size nitro trainer that may be out of control (new pilots can lose control of a plane in a hurry) and you're looking at a disaster looking for a place to happen.