All I know is that here in the northern Virginia/DC area, mud sharking isn't nearly as common as I've seen other places. I work with a black guy who keeps an online profile on yahoo dating. He's always complaining as he looks thru all the profiles that almost none of the non-black women (which includes asians and latinas) list black men as the type they are looking for. I've stood over his shoulder as he scrolled thru them. I was happily surprised to see he wasn't kidding.
Also, there are places in the area that everyone knows are white areas to hang out as far as clubs/bars. You will often find noticeable more black and minority women at these places than black men. Reason being, they're looking for white men.
My guess is, some white girls really want to rebel when they're young and date the guy their dad would hate the most. Eventually they screw their heads on straight and come back. Hell, even Madonna came back.