I'm beginning to think that there have been more fictional cases of amnesia than real ones.
Not that I blame the writers. Amnesia is a brilliant device. What is identity? How do you know who you are if you can't remember?
Americans move frequently. Our identity is not tracked by our neighbors, as it would be in small and more stable towns. These days, electronic reports follow us. Credit records, lists of traffic infractions -- somehow these seem to leave out the essentials of a person. Even if you have one of those supermarket club cards, tracking your grocery buys, your personality -- what is essentially you -- may not be contained in analysis of your purchases. There has to be more.
In many amnesia stories, the protagonist loses his or her memory and becomes a better person. This has to be reassuring -- we don't want to think that when the skill that makes someone a doctor or the shared past that held a relationship has gone there is nothing to replace it.
And, your identity makes a compelling MacGuffin. If it's lost, what is more urgent than to regain it? What would you risk or sacrifice to know who you are?
By its suddenness, amnesia makes a more dramatic story than the slow reforming, day by day, and choice by choice, that is the way we make our own identities.