I think of it as a two-dimensional market segmentation perspective: gender on one dimension, race on another. In a lot of segments, almost everybody is fighting it out in the "white guy" quadrant or at least the "guy" half. Take the Q&A space, for example: Quora is 80-90% guys, and so is StackOverflow. So there's room for competitors targeting the "niches" that actually make up most of the population. And there are similar dynamics in most market segments ...