I'm writing for an amnesiac protagonist, in spite of the fact that I feel amnesia in fiction is usually a bad cliché used to avoid some of the background work of creating a character's family, friends, hometown, career, etc. Ideally, I'd like to hear an answer from someone who has written an amnesiac character before, and struggled with this same "interesting vs cliché" problem. How do you make the character's amnesia something interesting and engaging for your audience? How do you avoid making your audience groan? What kind of problems do you throw at your heroes? I'm more interested in plot considerations than character considerations. Examples of successful properties are appreciated.
Why I'm using amnesia: My big bad has used magic to (accidentally) cause the amnesia in the protagonist and his allies, and that's what causes them to become involved. I intend for all of the amnesiacs to have fully realized histories that may or may not come up down the road, but I don't have those histories created yet.
On realism and offense: This is magically-induced retrograde amnesia according to the typical trope - the characters might remember their names, they remember how the world works and retain their physical skills, but they don't remember their past. (They may recover it over time, but may not) I am not overly concerned with medical accuracy - this is magic, after all. I am aware that amnesia is a real problem that real people have to deal with, but this story is not about that, and is more aimed at entertainment than education. I do not intend to offend anyone - I'm just not aiming for that kind of depth here.