In March, I wrote here and here about Obama's sudden interest in AGIA. There was talk that he was trying to funnel federal money into it, turning it into a "federal works project." My fear at the time was that he was going to swoop in and pretend that Palin wasn't running it successfully, take it over as one of his federal energy projects, and then take credit for its success (because Palin already did everything right and all the hard work in the first place). He could say that Palin needed help in getting it done and use that in his campaign if she ran against him in 2012. But she didn't need any federal input or money to get it done, thankyouverymuch. She started working on it the first day in office and everything was complete by the time she left.
So an added bonus of her resignation at this time is that the pipeline is up and running, the contracts and players are in place, the financials are all worked out, everything is done and now it just has to run its course. Obama can't say anything about having a hand in this. This is all Palin's accomplishment and will forever be. When she sets out to do something, it gets done. Unlike the President who voted "present" whose ideas turn out to be monumental failures - Palin will always have this as her crowning success, and she got it done in less than one term.