Whatever motivated Sarah Palin's resignation - and from her spooked look during her speech I suspect it wasn't a willing or happy choice on her part - I wouldn't count her out as a force to be reckoned with in future as some are already doing. There may be some kind of scandal about to erupt or maybe there isn't. I don't think it matters much as far as the impact she's likely to have from here on in is concerned.
First, let me say I think she's a sociopath, at the very least, if not a psychopath. She says the things she thinks she needs to say to get through whatever situation she's in and doesn't worry about matching that up with the facts or with consistency even to her own statements. Lying at the epic level she's done is a major red flag, as is the ruthlessness of her dealing with both opponents and supporters she no longer has a use for. The bloggers and others who used her lies and hypocrisy and her lack of knowledge about national policy during the 08 campaign to destroy her credibility with mainstream voters did a pretty thorough job of it. The only way she could possibly have come back from the drubbing she got was by going back to Alaska and showing herself to be a competent governor who eschewed drama and by spending the next couple of years heavily boning up on the issues. Obviously, she decided not to do that, for whatever reason. (I'm not one who thinks she was incapable of it; I think she's actually quite intelligent...as are many psychopaths.)
But then her real base has never been those who could be swayed by facts or rational argument. She always appealed most strongly to the portion of the population that operates in a belief-based manner rather than on the basis of evidence, facts, and reason. It's the same demographic that finds Rush Limbaugh a compelling political pundit or Joe the Plumber an authoritative reporter on the Middle East.
If that's the direction she chooses to go from here - a Fox News commentator, talk radio host, political columnist, author - she'll be far more free to speak and act as she wishes than she is now, under the restrictions imposed by being an elected official. Her power as the governor of such a relatively unpopulated and remote state was quite limited anyway, except for its usefulness in launching her onto the national stage.
As a politico-cultural commentator she'll have more credibility than Limbaugh (as a major party's VP nominee just a few short months ago) and certainly more attractiveness, especially to a politically naive audience, among which I'd count a large portion of the American electorate, who are more swayed by a politician's individual characteristics such as perceived integrity and personal attractiveness and by a shared tribal identity than by an understanding of their political ideology or its implications.
Obama hopes to heal the political polarization that is destroying the country, and he's willing to compromise his agenda, even health care, one of his top domestic priorities, to get the bipartisanship he thinks is needed to overcome the polarization. I think he's wrong on that - success in his policies and showing that progressive solutions are the ones that have the most benefit to people in their everyday lives are what will end this cycle of polarization.
What concerns me is that while Sarah Palin was not very good as a national-level politician, she is likely to be very good as a full-time political culture warrior and rabble rouser who will dial up the level of polarization for all she's worth. Her content-impaired jingoism will fit right in with national media that already accepts the likes of Limbaugh, Beck, Coulter as worthy of being given access to national audiences instead of marginalized as the fascist monsters that they are. She'll be given ongoing support on the national stage by a cynical ratings-seeking and braindead celebrity-worshipping media. It will be one more circus with a new loudmouth star clown in the ring.