NY Times had a very interesting article concerning this issue, entitled "Queer as Folk", back in August of 2002:

http://query.nytimes.com/gst/abstract.html?res=F20814FC3B5E0C7B8DDDA10894DA404482

Unfortunately, you will need to pay $2.95 to read beyond the second paragraph. Sheez. Maybe we Mudcatters can take up a collection to view it, because it is a good read...although Dar Williams took offense to it, because it suggested that she was remaining mysterious about her orientation so as to consolidate a solid fan base that would include many lesbians (she has since married a man).

I also seem to remember it mentioning that folk music is the unofficial genre-of-choice for lesbians, and disco the genre-of-choice for gay men.