Here is my take and it was shaped by an article I read yesterday. I started to bring this up the other day wes, but I figured Tarheel would beat me to it.
From the article the author mentioned something that made a lot of sense. She came from a middle class background and her husband, who has a good paying job, is not necessarily knocking down the big bucks. The Palin's don't have the nest egg that most prominent politicians (pres, senators, congressmen, gov's...etc...etc) have and that the legal battles she is in has already cost her somewhere around $500K to $750K in lawyer fees. Some company out there might have offered her a job (read: $$$$$) she can't really pass up and thought it was best for her family. Is it true? I don't know but it makes a little sense.
He also pointed out and as Sani said, she may be tired of the bullshit. You have to admit that the MSM and the DNC went after her hard and turned her life upside down. They even went as far as to claim that her "special needs/retarded" (call it what you want) was really her grandchild. It is now 8 months past the election and the MSM and DNC are still hounding her and dragging her through the mud. What gives? Are they afraid of her that much? The only thing I can think of is that they are afraid that she will either seek a Presidential nod down the road or they are thinking that she will run for the House or Senate and become a player on the national level.
I tend to agree a little with what the guy was saying. It might be both, it might be that the legal battles are becoming too expensive for someone with not that much of a nest egg on a governor's salary and the bullshit she has had to deal with over the past 10 months or so.
I liked somethings about her and somethings I did not. I still don't think she has a big enough machine behind her to make a push for the White House in 2012. I think she knows that as well and I don't think she would step down mid term to prepare for a run.