Just because you haven't seen one (or remember one) doesn't mean it hasn't or won't happen. Maybe you just aren't looking for it.
You're kidding right? I sit in waning hope that some Protestant will jump in and clean up messes because I know as soon as I pipe up ears, eyes, minds and hearts will shut simply because I'm a Catholic.
I sat here praying someone would address the Trinitarian/Incarnation confusion because I knew my stuff was just bouncing off the walls... it didn't happen. I reached the conclusion that trinitarian "heresy" just doesn't matter among American Protestants anymore because apparently as long as someone has a fuzzy belief that Jesus is the Son of God and doesn't approach Mormonism on the one side or Oneness Pentecostalism on the other then nothing matters. Although I think there are some Oneness people around who never get called on it by the "usual suspects" either.
I really believe that if I were to compile a list of the ancient heresies as formulated by the heresiarchs themselves and said "ok now, who adheres to any of these" people would come out of the woodwork to claim their particular peculiar beliefs, stare at each other and say nothing. But if I added "oh, and who here believes it is right to call Mary the Mother of God" all hell would break loose.
"Weird" beliefs don't matter around "here" as long as those weird beliefs don't smell of Catholicism.