Elaborate character histories, basically small works of fiction starring the player's character, I see no point in. All they do is supplant the function of the actual campaign. What I do want from my players, however, is a backstory that explains why they're an adventurer. "Small town background, wanted to see the world" is sufficient. For the purposes of the campaign, neither I nor the player needs an elaborately crafted set of events, just a basic character sketch to start roleplaying with. Interesting, deep characters will emerge from the decisions they make over the course of the game. Endless preplanned detail tends to just get in the way.