Women outnumber men on social networking sites by a substantial margin across all age brackets - both in terms of number of participants, as well as average time spent.
A related thought is that perhaps the tide is turning on the great "shortage of women in technology." Men have dominated computers, electronics, and video games for decades. It has often been lamented that there aren't any good video games for women and girls, and my electrical engineering courses in the 1990s were certainly laughable - more than 90% of my classmates were men.
Social networking might just be the video game that women have been waiting for.