Let's not forget that Obama pledged to transcend negative politics and run a positive campaign at the beginning as well. He has also broken that promise.
Nobody has called him a terrorist. They are, however, pointing out his poor judgment in his choice of the company he keeps. I think it's fair game.
Conversely, if the Obama Campaign wants to focus on Palin's previously friendly ties with the Alaska Independence Party and McCain's ties to Keating, all the more power to them. Once they've opened up those doors, it's all fair.
It has recently been revealed that Bill Ayers and Obama had a closer relationship than just "a guy from my neighborhood". They weren't best buddies, but it was closer than Obama had initially described it as.However with the economic crisis, it was kind of drowned out. I think Americans have a right to know the kind of associates the candidates ---all the candidates---keep. Then they can judge for themselves.