As for Obama, there are many people who have spent a good deal of effort to link his name to all kinds of things. None the less, when I search for 'Obama' I don't get a website about Socialist Muslims as my top link. The difference is that Obama is a generally respectful human being as politicians go. Santorum brought this on himself in a way that someone like Obama simply never will. If more people rolled their eyes at the definition, than those who gave it a nod, it wouldn't be #1.
Santorum's problem, not Google's.