I've mentioned before that I think one of the reasons it's important to say "lesbians and gay men" rather than just "gay people" is that in mixed groups women get ignored. We need to really let people know we're there, and even then often men predominate.
I've illustrated this concern before by talking about same-sex marriage. Although every locality that has begun to legally recognize same-sex marriage has experienced the same gender pattern - many more women marry than men - the focus and the pictures in news stories are much more often m/m couples.
Another example from this morning's NY Times is here. It's an article on the Massachusetts experience entitled, "Gay Couples Find Marriage is a Mixed Bag." The article clearly states that 2/3 of the legal same-sex marriages in Massachusetts are women. And the photos? A male couple, then a female couple, then a man (with a caption about him and his husband), then a male couple. Hmmm. Real marriages - 2/3 women. Pictured marriages - 3/4 men.