She is likely to lose a Republican primary and she is likely to lose a Democrat primary and she cannot win as a "third party".
Palin is in an enviable position right where she is. Why spoil it?
To watch the Dims twist themselves in knots and waste tons of campaign cash would be worth it IMO. The icing on the cake would be watching the democrats chuck the popular vote via the super delegate option.
Not to mention turn about is fair play til they change the rules. Dims crossed over in massive #s to stick us w/ McLame.