Often called “bug chasers” among the gay community, these men seek out other gay men who are infected, in hopes of having unprotected sex, barebacking, in an effort to become infected with HIV. Across the Internet, chat rooms and newsgroups are advertising “conversion parties” where negative men seek out those who are positive in hopes of getting infected. This practice of having deliberate unprotected anal sex has the potential to cause widespread HIV infection, especially among gay men and men who seek out anonymous sexual partners on the Internet
Fantasies of HIV Infection - Not Just an Urban Myth
http://aids.about.com/od/safersexresources/a/barebacking.htm