Violet Blue, who was one of the earliest porn bloggers and reviewers (check out her blog, TinyNibbles), reports on Oprah.com that women are becoming an increasingly large segment of the porn market. This trend is a longtime coming, but it's good news nonetheless.
I agree with Violet's claim that poor quality and social stigma are the largest detractors for potential female customers. Body image issues are also a detractor. At least some producers recognize the need to listen to their market (a novel concept to some in the industry):
As the porn industry suffers at the hands of free Internet content and customer ADD, finding and appealing to new markets will be the key to survival. For too long, it has been easy to make money churning out low-quality content, since consumers had few alternatives and tended to buy whatever was available. I foresee a shift towards quality and consumer targeting, and women--those age-old consumer behemoths--will be the savior of many porn companies.