A tad reactionary?
People gotta relax. I'm assuming that you've read the cynical blurb at MacSlash and have assumed something much more sinister is going on. I read it too, and thought "where is this person coming from?" I think the cynicism is unwarranted. This is after all, trademark protection, the law. If you don't protect it, you lose it (future attempts to protect the trademark would be much more difficult if not impossible), and then where would a smaller developer be without intellectual rights? So, considering the obligation to protect the trademark, and considering this conference targeted Mac users that use graphics software, this seems like a fair context to enforce the trademark. IDG could have just as easily challenged Stone in court over dilution of trademark/generic brand, like "aspirin," and God knows they have the resources.
Also note that Stone didn't make money with this decision. :-)