This word has been tainted in the last several years. Yes, there are some people who are genuinely attracted to both males and females, which is fine. There is also this MTV-styled movement among young people, particularly females, who feel the need to act this way in public just to earn some cheap attention from men (most likely they grew up with no father so this is what they do to fill that void). They will especially act it up in bars or any gatherings where males are plentiful. Being loud at the same time to make sure the people whose backs are turned happen to turn around is also a must. Of course they don't ever engage in such behavior with the same friends when not in public or if, say, older people happen to be around. It's just a convenience factor and it strokes their ego when men hoot and holler at them for selling out their dignity.
PuNkGrRrLnUmBeR1: Hey look, those guys are checking us out! Quick, kiss me and fondle my boobs!
PuNkGrRrLnUmBeR2: Oh kewl! That'll make them talk about us and whip out their camera phones! Let's do it!
Typical behavior of "bisexual" females in bars.