I don't think how many books one's sold or how many are willing to pay you to speak to an audience always a good measure of significance. Jersey Shore anyone?
Coulter is paid to ruffle feathers sometimes, so her more abrasive personality I usually attribute to that kind of obligation to her "brand". Which of course, help her aforementioned book sale and public speaker engagements.
Doesn't mean she's always wrong or right, but you're gonna have a lot of people that are turned off by her and strangely enough, that actually brings in more attention.