My child says that, it means two things.
1) That word has been used enough times in front of kid, to make kid learn it.
2) That kid said it without flinching. There was no testing. Kid knew he'd get away with it.
Now, I am not going to shit on palin for her parenting. Her politics, hypocricy, sure. THis is poor taste and shows she doesn't have control of the situation, but tough to hate on her. I can tell ya my kid woudl have a spanking for using that kind of language, but it wouldn't have been modeled in the first place. Palin sucks, but this is a footnote (probably released to keep her show from being cancelled as it has had terrible ratings)