I think only a tiny minority of lesswrong readers, believe in cryopreservation. If people genuinely believed in it then they would not wait until they were dying to preserve themselves, since the cumulative risk of death or serious mental debilitation before cryopreservation would be significant, the consequence is loss of (almost) eternal life,
Humans are not totally rational creatures. There are a lot of people who like the idea of cryonics but never sign up until it is very late. This isn't a sign of a lack of "belief"(although Aris correctly notes below that that term isn't well-defined) but rather a question of people simply going through the necessary effort. Many humans have ugh fields around paperwork, or don't want to send strong weirdness signals, or are worried about extreme negative reactions from their family members. Moreover, there's no such thing as "almost" eternal life. 10^30 is about as far from infinity as 1 is. What does however matter is that there are serious problems with the claim that one would get infinite utility from cryonics.
If people were actually trying to preserve themselves early then there would be a legal debate. There is none (unless I'm mistaken).
There have been some actually extremely tragic cases involving people with serious terminal illnesse such as cancer having to wait until they died (sometimes with additional brain damage as a result). This is because the cryonics organizations are extremely weak and small. They don't want to risk their situation by being caught up in the American euthanasia debate.
What is the real probability? I think given the lack of success of humans in making long term predictions suggests that we should admit we simply don't know. Cryopreservation might work. I wouldn't stake my life, or my money on it, and I think there are more important jobs to do first.
This is one of the weakest arguments against cryonics. First of all, some human predictions have been quite accurate. The main weakness comes from the fact that almost every single two-bit futurist feels a need to make predictions, almost every single one of which goes for narrative plausibility and thus has massive issues with burdensome details and the conjunction fallacy.
In looking at any specific technology we can examine it in detail and try to make predictions about when it will function. If you actually think that humans really bad at making predictions, then the you shouldn't just say "we simply don't now" instead you should adjust your prediction to be less confident, closer to 50%. This means that if you assign a low probability to cryonics working you should update towards giving it an increased chance of being successful.
"The main weakness comes from the fact that almost every single two-bit futurist feels a need to make predictions, almost every single one of which goes for narrative plausibility and thus has massive issues with burdensome details and the conjunction fallacy." - no. The most intelligent and able forecasters are incapable of making predictions (many of them worked in the field of AI). Your argument about updating my probability upwards because I don't understand the future is fascinating. Can you explain why I can't use the precise same argument to say there is a 50% chance that Arizona will be destroyed by a super-bomb on January 1st 2018?
If an American signs up for cryonics and pays their ~$300/year, what are their odds of being revived? Talking to people at LessWrong meetups I've heard estimates of 1 in 2. My friend George Dahl, whose opinion I respect a lot, guesses "less than 1 in 10^6". Niether has given me reasons, those numbers are opaque. My estimate of these odds pretty much determines whether I should sign up. I could afford $300/year, and I would if I thought the odds were 1:2, but not if they were 1:10^6. [1]
In order to see how likely this is to work, we should look at the process. I would sign up with a cryonics company and for life insurance. I'd go on living, enjoying my life and the people around me, paying my annual fees, until some point when I died. After death they would drain my blood, replace it with something that doesn't rupture cell walls when it freezes, freeze me in liquid nitrogen, and leave me there for a long time. At some point, probably after the development of nanotechnology, people would revive me, probably as a computer program.
There's a lot of steps there, and it's easy to see ways they could go wrong. [3] Let's consider some cases and try to get probabilities [4]:
Update: the probabilities below are out of date, and only useful for understanding the comments. I've made a spreadsheet listing both my updated probabilities and those for as many other people as I can find: https://docs.google.com/spreadsheet/...
Combined Probability Of Failure: 99.82%
Odds of success: 1 in 567.
If you can think of other ways cryonics might fail, moving probability mass from "other" to something more quantifiable, that would be helpful. If you think my numbers are off for something, please let me know what a better number would be and why. This is not final.
Am I going about this right? Do people here who think it's rational to sign up for cryonics take a "the payoff is really high, so the small probability doesn't matter" view? Am I overly pessimistic about its chances of success?
Note: I originally posted this on my blog, and the version there has a silly javascript calculator for playing with the probabilities.
[1] To figure out what odds I would accept, I think the right approach is to treat this as if I were considering signing up for something certain and see how much I would pay, then see what odds bring this below $300/year. Even at 1:2 odds this is less effective than Village Reach at averting death [2], so this needs to come out of my 'money spent on me' budget. I think $10,000/year is about the most I'd be willing to spend. It's a lot, but not dying would be pretty nice. This means I'd need odds of 1:33 to sign up.
[2] Counter argument: you should care about quality adjusted life years and not deaths averted. Someone revived maybe should expect to have millenia of life at very high quality. This seems less likely to me than just the claim "will be revived". A lot less likely.
[3] In order to deal with independence issues, all my probability guesses are conditional on everything above them not happening. Each of these things must go right, so this works. For example, society collapsing and my cryonics organization going out of business are very much not independent. So the probability assigned to the latter is the chance that society won't collapse, but my organization goes out of business anyway. This means I can just multiply up the subelements to get probabilities for sections, and then multiply up sections to get an overall probability.
[4] This has a lot in common with the Warren formula, which was inspired by the Drake equation. Robin Hanson also has a breakdown. I also found a breakdown on LessWrong that seems really optimistic.
EDIT 2011-09-26: jsalvatier suggested an online spreadsheet, which is very sensible. Created
EDIT 2011-09-27: I've updated my probabilities some, and made the updates on the spreadsheet.