At some point in the future, we hope, brains which have been cryonically preserved may be resurrected, by some process of neural reconstruction (most likely either as nanotech, reconstituted wetware, or virtual simulation).
Imagine that the technology has just come available to resurrect a frozen brain. However, the process has low fidelity, due to resource and technique limitations. Luckily, these limitations are purely practical - as the technique is refined, the process of resurrection will become better and better. The process is also destructive to the original preserved brain, so there's no going back and making a second, higher-quality scan.
The results of the process is effectively a copy of the old brain and personality, but with permanent brain damage in several regions - this manifests effectively as an extreme form of cerebral palsy, partial amnesia (retrograde and anteretrograde), bipolar disthymia, and a partial frontal lobotomy - in short, you'll get something that has recognizable facets of the original, but it's an utter mess.
As the technology progresses, each of these symptoms will be lessened, until eventually they will be effectively eliminated altogether. However, the first few thousand subjects will suffer irrecoverable memory loss and will suffer a horrifically low quality-of-life for at least several decades until the technology improves.
The technology will not progress in refinement without practice, and practice requires actually restoring cryogenically frozen human brains.
Let's establish a metric so we can talk numerically:
0.000 - complete and persistent vegetative state, aka dead (this is our current state of progress in this technology)
0.100 - Terry Schiavo (persistent vegetative state with occasional non-conscious responses)
0.500 - the equivalent of advanced Alzheimer's syndrome; severe mental and physical impairment
0.700 - moderate mental and physical impairment
0.800 - significant reduction in facilities (IQ loss of 20 to 35 points, severe difficulty with memory, slurred speech, frequent and severe mood swings)
0.900 - slight reduction in facilities (IQ loss of 10 to 20 points, moderate short- and long-term memory loss, frequent but moderate mood swings)
0.950 - liminal reduction in facilities (IQ loss of 5 to 10 points; occasional slowness in memory recall, occasional mood swings)
1.000 - a perfect reproduction of your original personality and capability
QUESTION 1: If your brain was frozen, at what stage in this technological refinement process would you like your brain to be revived?
QUESTION 2: If you had had your brain preserved before anyone had asked you this question, how could the reviving technicians ethically know this value? Remember that they cannot thaw you to ask you.
QUESTION 3: Assuming as part of this what-if that the technology cannot progress past 0.500 fidelity without human trials, who should we attempt to revive when the technology is at 0.500? At 0.7? 0.8? 0.9? 0.95? Assume that we haven't asked any of the subjects this question, so we do not know their own preferences.
Question 1: This depends on the technical details of what has been lost. If it merely an access problem: if there are good reasons to believe that current/future technologies of this resurrection society will be able to restore my faculties post-resurrection, I would be willing to go for as low as .5 for the sake of advancing the technology. If we are talking about permanent loss, but with potential repair (so, memories are just gone, but I could repair my ability to remember in the future) probably 9.0. If the difficulties would literally be permanent, 1.0, but that seems unlikely.
Question 2: Outside of asking me or my friends/family (assume none are alive or know the answer) the best they could do is construct a model based on records of my life, including any surviving digital records. It wouldn't be perfect, but any port in a storm...
Question 3: Hm. Well, if it was possible to revive someone who already was in the equivalent state before cryonics, it would probably be ethical provided that it didn't make them WORSE. Assuming it did... draw lots. It isn't pretty, but unless you privledge certain individuals, you end up in a stalemate. (This is assuming it is a legitimate requirement: all other options have been effectively utilized to their maximum benefit, and .50 is the best we're gonna get without a human trial) A model of the expected damage, the anticipated recovery period, and what sorts of changes will likely need to be made over time could make some subjects more viable for this than others, in which case it would be in everyone's interest if the most viable subjects for good improvements were the ones thrown into the lots. (Quality of life concerns might factor in too: if Person A is 80% likely to come out a .7 and 20% likely to come out a .5; and Person B is 20% likely to come out a .7 and 80% likely to come out a .5, then ceteris paribus you go for A and hope you were right. It is unlikely that all cases will be equal.)