As a former member of a professional quilt association I can see both sides. With the advent of the longarmers the biggest problem I see is that their work is not being credited to them. I have a friend who is also a handquilter for hire. She did a quilt for a woman who won first place for "handquilting" at Paducha. The problem was she failed to tell the judges that it was not her work. When my friend objected the customer replied that she had paid her so the work belonged to her.
I do believe that once your quilt is published in a commercial magazine all bets are off. As long as you don't sell it claiming that it was your original design I don't see how they could object. To me it is like actors that are so upset about their pictures being published. They need to remember that it is free publicity and conduct themselves accordingly in public. I do make it a point to give a designer credit if I enter or show a piece that uses their design.