I think most folks are over-thinking this. Lets stipulate that I have lost my memory for whatever reason. All my passwords are generated using a relatively simple pattern. If I was amnesiac, I still have all those passwords saved in my browser, chat and email clients. Amnesiac me can collect email and log into sites that I use as long as my computer is intact. My wife knows the pattern but not the current passwords, if I can't get into the password lockers, my wife can give me the starting point. From there I can access my passwords with as little as 5 tries. However, as long as my email client still has useful passwords, the vast majority of my password list can be reset with a simple "I forgot my password" request. If, for whatever reason, those two options aren't good enough, I really don't care y'know? If I'm amnesiac, I have much bigger problems on my plate than whether I can access any social sites, member-only areas of sites and so on. Given the kind of brain trauma needed to get significant amnesia, I probably would not have much use for email for the first while anyway.
I agree with this method. My wife knows the basic password and the basic pattern. With her help I could figure it out in less than 10 tries. She is an admin on our network and can manage that but the only password she does not have and that does not comply with out pattern, is our encrypted drive. Never really thought about loosing or forgetting that password. Not too concerned about it either. I could switch it to our pattern and then apply a key file from a file on our network. She and I would know which file was the key file. Eventually (and probably already) everyone loses data. My data loss in the past has been insignificant, fortunately.
There must be more to life than having everything. -- Maurice Sendak