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. 
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.  Let's consider some cases and try to get probabilities :
Update: the probabilities below are out of date, and only useful for understanding the comments.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/...
|0.03||You mess up the paperwork, either for cryonics or life insurance|
|0.10||Something happens to you financially where you can no longer afford this|
|0.06||You die suddenly or in a circumstance where you would not be able to be frozen in time (see leading causes of death)|
|0.04||You die of something like Altzheimers where the brain is degraded at death (Altzheimers is much more common than brain cancer)|
|0.01||The cryonics company is temporarily out of capacity and cannot actually take you, perhaps because lots of people died at once|
|0.02||The life insurance company does not pay out, perhaps it's insolvent, perhaps it argues you're not dead yet|
|0.02||You die in a hospital that refuses access to you by the cryonics people|
|0.02||After death your relatives reject your wishes and don't let the cryonics people freeze you|
|0.10||Some law is passed that prohibits cryonics (before you're even dead)|
|0.20||The cryonics people make a mistake in freezing you (how do we know they don't make lots of mistakes?)|
|0.20||Not all of what makes you you is encoded in the physical state of the brain|
|0.50||The current cryonics process is insufficient to preserve everything|
|0.35||Other (there are always other things that can go wrong)|
|0.86||Something goes wrong in getting you frozen|
|0.30||All people die (nuclear war? comet strike? nanotech?)|
|0.20||Society falls apart (remember this is the chance that society will fall apart given that we did not see "all people die")|
|0.10||Some time after you die cryonics is outlawed|
|0.15||All cryonics companies go out of business|
|0.30||The cryonics company you chose goes out of business|
|0.05||Your cryonics company screws something up and you are defrosted (power loss, perhaps. Are we really expecting perfect operation for decades?)|
|0.80||Something goes wrong in keeping you frozen|
|0.10||It is impossible to extract all the information preseved in the frozen brain|
|0.50||The technology is never developed to extract the information|
|0.30||No one is interested in my brain's information|
|0.40||It is too expensive to extract my brain's information|
|0.03||Reviving people in simulation is impossible|
|0.20||The technology is never developed to run people in simulation|
|0.10||Running people in simulation is outlawed|
|0.10||No one is interested running me in simulation (even though they were interested enough to extract the neccesary information from my frozen brain)|
|0.05||It is too expensive to run me in simulation (if we get this far I expect cheap powerful computers)|
|0.93||Something goes wrong in reviving|
|0.05||Something else goes wrong|
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?
 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 , 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.
 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.
 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.
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.