A few people have commented to the effect that this is a tempest in a teapot, but the phenomenon of copyleft trolling is news to me. It's fundamentally contrary to the spirit of Creative Commons and like-minded licenses, and has a chilling effect on their use. Cory claims that another of Pixsy's clients, Marco Verch, single-handedly shuttered a Dutch charity.
I've never paid much attention to the Creative Commons version numbers. I sure will now.