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.