Several years ago I read "Black Lies, White Lies: The Truth According to Tony Brown." Part of his book argues that AIDs is not a heterosexual disease. Very, very interesting. He said, based on some evidence, that blood transfusions, intravenous drug use, and third world health conditions are the primary ways the disease is spread. The disease became rampant in the gay community, according to Brown, because of the sexual practices of many gays was so indiscriminate and random, involving multiple partners, etc. that they wound up contracting numerous STDs, which greatly impacted their immune system. He cited and quoted a gay guy who frequented the bath houses in SF and this guy had like ten different STDs and other illnesses related to his sexual practices.
If I recall correctly, he said you really can't find cases where a heterosexual contracts the disease through normal sex with another heterosexual. And that when those cases do arise, one of the partners got it from someone who fits the profile (blood transfusions, intravenous drug use, third world health/sex conditions).
I balked when I first read his theory, but after reading the entire section and thinking about it, I think it makes sense. Can't find the book, but I'm going to buy it again and try and quote the passages I read if this thread hangs around long enough.