This is a damn good question. I don't know any anti-bitcoiners who've made good cases for why Bitcoin could fail. I just see the usual refuted FUD coming from anti-bitcoiners.

I know this doesn't exactly answer your question, but I've heard a few couple podcasts from Bitcoiners who are concerned about the community becoming overconfident. They presented some cases where Bitcoin could fail or just fail to meet our expectations. Here are the episodes if you want to check them out: