[pvaldes]

It can matter a lot. The arrival of HIV in 80's changed suddenly how people interact with sex forever. Specially one night stands and casual sex. I can do some damage control about who enters in my partners list, I don't have any control about who were in yours so yes, sometimes it matters.

[ProjectArcturis]

If you're a man who has sex exclusively with women who are not prostitutes and do not use IV drugs, your odds of contracting HIV are vanishingly small.