Thanks for the information, but that suggests that preserving a human brain will be difficult and may require more advanced techniques than currently used, not necessarily that it's some crazy impossible thing that shouldn't even be thought about. Hell, maybe it would be possible to carefully cut up the brain into smaller chunks before freezing it (a sharp cut along the right line being perhaps not so damaging compared to bad freezing).
A lot of it is going to come down to exactly how memories are stored and how redundant they are. Last time I checked this wasn't yet fully understood. If they really do depend on fine details of molecules that are inevitably irreversibly scrambled by freezing, then it probably is impossible after all.
I don't think anybody is claiming that viable brain preservation will be necessarily forever impossible. The claim is that brain preservation as currently offered by cryonics comapanies is probably flawed and unlikely to maintain the relevant aspects of somebody's personal identity.
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.