I think it's important to note though that Scarlett O'Hara wouldn't probably work as a character if Margaret Mitchell wasn't such a damned good writer. There's a real fine line between characters who are jerks and yet still great characters, and characters who are jerks and are just annoying.

I think two things really make the difference:

1. The author knows that their character is a jerk, instead of thinking they're the coolest thing ever...

which leads to:

2. The author has everyone else in the novel react in a realistic way to said jerkiness.

And that's the difference between an awesome character like Scarlett O'Hara and an annoying character like Anita Blake. Anita Blake is also a raging bitch, and yet Laurel Hamilton seems to think she's not, and it's reflected in the writing by the way the other characters unrealistically react to her (i.e. all want to have sex with her or are total jealous bitches/villains). I can't tell you how many times I've read a novel think "Damn, this would be sort of awesome if the author realized what a bastard this character is and rolled with it" and have instead tossed the book against the wall after the character has been a total asshole, and yet everyone thinks they're the greatest/nicest/most awesome thing ever.