I don't think the C&D letter was designed to stop the pin craze. I think it was a warning to stop using trademarked and copyrighted material on the pins. I agree the lawyers hand was probably forced when someone complained.
As long as the pins are kept legal I don't see any reason to stop the hobby. That's why I don't understand why a board would shut down pin talk.
I'm so glad to see so many pin people trying to get back on track and have fun again.