Well I've been on these forums a while and I have serious doubts that all the "heterosexual" posters in the "what sexuality are you?" and "what do you find attractive" kinds of threads are actually straight.
/satire
OP, way to be condescending. You have no right to point a finger at people and say, "hey, you know what, I hear bisexuality is very trendy right now. Therefore, most bisexuals are just making shit up. lololol my learnings." That's exactly like saying, "I hear Buddhism is very popular right now thanks to Richard Gere. Therefore most if not all Buddhists are just faking to be cool."
True, there is a stage during teenage years when the body doesn't know what the hell is going on, and some teens label themselves as bisexual because they honestly believe they are. And yes, there are always going to be some people who claim they are something - bisexual, whatever - to impress or shock other people. But that does not mean you can wander into a forum and accuse everybody of lying based on the stereotype that bisexuals are trendy. I'm bi, and I'm the least trendy person I know. And I'm not attracted to men and women purely because I think it's awesome - it's just the way I am. Like a lot of bisexuals.