Note that in general low-transmission rates aren't that good an argument against it. First of all, a lot of transmission in the US occurred through other forms, especially early in the epidemic (intravenous needle sharing and transfusion of infected blood being two major ones). As others have noted the transmission issue is also generally higher for homosexual rather than heterosexual intercourse.
Frankly, the thing that I most don't understand about people who are skeptical about the HIV-AIDS link is how one explains the fact that anti-virals tailored to deal with HIV work. Even the first-gen treatments such as AZT were used due to the biochemistry of HIV (often targeting reverse transcriptase). And they worked in delaying the onset of AIDS and worked for giving people with AIDS higher life-expectancy. I don't see how one can easily reconcile that with HIV not being the cause of AIDS and I've never heard anything remotely resembling a coherent explanation about this.
The extremely low official transmission rates indicate that HIV is probably not a sexually transmitted disease, as typically understood. According to the published transmission data, it's only effective natural means of transmission is vertical - from mother to child. From what we know about symbiosis and parasites, this should lead one to suspect it is not that lethal.
However that doesn't destroy the hypothesis that HIV could be a unique disease of civilization - a mutation of a formerly limited retrovirus into a more damaging form that spreads horizont...
This thread is for the discussion of Less Wrong topics that have not appeared in recent posts. If a discussion gets unwieldy, celebrate by turning it into a top-level post.