The phrase "gay and lesbian" in the names of our organizations has apparently completed its evolution to "gay, lesbian and bisexual." The next step, no doubt, will be to adopt the French construction and label ourselves, collectively, "gay, lesbian, bisexual and bisexuelles," to differentiate between males and females attracted to both sexes. Overparticularizing hurts our image. Presenting ourselves as a coalition of three subgroups suggests to the standard All-American bigot a kabal of "special-interest groups" (as conservatives call us). It presents three "ugly" words to be assimilated, instead of one—three "fringe" groups to be accommodated.
Source: wiktionary