When I've brought up cryonics on LessWrong [1][2], most commenters have said I'm being too pessimistic. When I brought it up yesterday at the Cambridge MA meetup, most people thought I was too optimistic. (I think it could work, but there are enough things that could go wrong that it's ~1000:1 against.) What makes the groups so different on this?
"Pessimism" or "optimism" is a wrong way of describing the disagreement, there are important details missing in such broad a categorization, and if we don't agree on methodology of making the estimates, comparing the resulting numbers is useless. For example, How Likely is Cryonics to Work employed a mistaken independence assumption that makes the quantitative conclusion of the analysis meaningless (even as some of the intermediate steps are more informative).
It didn't:
There was some discussion of this on the post.