Cryonics will definitely fail if the peace-of-mind cryonicists dominate it instead of the serious adults who want to survive. 

You can see most cryonicists' fundamental lack of seriousness from the fact that they talk a good game about how much they believe in scientific, technological and medical progress. So what happens when you try to draw their attention to the many correctible shortcomings in the real, existing practice of cryonics? They usually shrug those off as if these problems don't matter.

Uh, hello?

This fundamental lack of an evidence- and reality-orientation in many cryonicists goes a long way towards explaining why mainstream people don't find the cryonics idea credible, much less its haphazard implementation. I just have no patience these days with cryonicists who invoke Eric Drexler's discredited fantasies from the 1980's, or who make fallacious comparisons between cryonicists and the Wright brothers. Cryonics falls into the overlap between neuroscience and cryobiology, and progress in it will have to come from the application of those real sciences.