Slate's Dahlia Lithwick hypothesizes why Sarah Palin really quit:
[W]hen the dust settles, the lesson may be that she was simply a woman who made no sense. Her meteoric rise and dubious fall will say less about America than you think, beyond the fact that America likes its politicians to communicate their ideas clearly. We will someday come to realize that while it's all well and good to be mavericky with one's policies, it's never smart to be mavericky with one's message.
...It's too easy to characterize Sarah Palin as an irrational bundle of bristling grievance. But I think it's more complicated than her simple love for playing the victim all the time. ... Think of an American visiting France who believes that if he just speaks louder, he will be speaking French. Palin has done everything in her power to explain herself to us, and still we fail to appreciate what she is all about. I'd be frustrated, too, if I thought I was offering up straight talk and nobody was getting the message. Especially if I held a degree in communications.
In any event, after this month, we won't have Dick Nixon Sarah Palin to kick around anymore.