The other hypotheses were located in similar manner, though. And far too much has to be ignored to generalize from said animal organs or said microscopic animals. Generalization from kidneys to brains is particularly dubious. Especially as great many of said frozen corpses are frozen corpses precisely because of their brain's unusual fragility with regards to loss of blood supply.
edit: The issue is not with cryonics in principle. The issue is with cryonics as it is. Similar to the people jumping off towers with some wings vs an airplane. Seeing a bird fly really doesn't make for a case that you can fly by your own muscular power with some homemade birdlike wings, with the early prototype, in fact it makes for the opposite case (as none of the birds are as heavy as you are). Evidence against a hypothesis can locate it too.
edit2: And with regards to information theory, it is absolutely trivial and clear cut: given that there is a mapping from a larger phase space, to a smaller phase space, meaning that some information is irretrievably lost. It is not there anymore for any super-intelligence to deduce. Just that. This summarizes everything information theory has to say about the issue. Whenever that information is important or not, that is a question of neurobiology.
With regards to the future cryonics, there's two possibilities:
1: Revival. If we can cryopreserve brain tissue, revive it, and it retains learning, that would be an indication that the procedure works.
2: Fixatives. The opposite of revival. If we find out how exactly the memories are stored, we can develop a fixative mix that would lock those proteins in place by cross linking, i.e. adding strong chemical bonds in place of weak intermolecular bonds. That is a drastic measure which would require pumping the brain full of highly toxic, carcinogenic chemicals such as formaldehyde. (This may even permit room-temperature storage, or may require cooling). Without knowledge of how it is stored one can make a shot in the dark and hope that particular fixatives would work.
Current cryonics is neither, and is hence not taken seriously by experts in any fields expertise in which is actually necessary for evaluating whenever the lost information is relevant. I've a nagging suspicion that an effective procedure for future uploading would end with a brain diced into small slices and stored at room temperature in a jar of some cheap cocktail of fixatives. With all molecules neatly cross linked in their original places rather than unravelled and detached by solvents.
Well, I'm mostly interested in brain/mind-preservation in general - I don't care if it's by fixatives or freezing. I've heard discussion of "plastination" which seems similar to your point #2. Even aside from whether it's more likely to actually work or not, it seems like it could be cheaper and more practical as well. I'm all in favour of more research along those lines.
(Earlier you gave me the impression that you thought the entire concept of preserving a brain was some wild fantasy not even worth thinking about (ie the typical opinion of Very Serious People), but this seems more like you were disagreeing with the effectiveness of cyroprotectants specifically, which I don't have strong grounds for an opinion on).
In the past, the Cryonics Institute has had a policy that said that they would not accept anyone who is not a member. This has changed. The policy now is that someone who has full legal authority over your body can sign you up after you die. It costs $36,250 to be frozen if you are not signed up, which is more expensive. They also will not do anything until you have been on dry ice for 2 weeks after they have been contacted, so not being a member is more risky.
This is very important news for anyone who is currently cryocrastinating. It means that you can drastically increase your chances of survival without filling out any forms. All you have to do is tell a loved one you want to be frozen upon death, and that you would like them to take responsibility for making sure this happens. This takes literally 30 seconds. Do it now!
This news might also be a reason to not sign up right away, if you think something better (like radical life extension or uploading) will come along in your lifetime. We should discuss this in the comments.
Edit: The general consensus of this discussion is that this is a really bad reason not to sign up for cryonics.