A generic term for a straight girl who lists their orientation on any site as 'bisexual' for attention. Mostly to attract otherwise homophobic straight men who think it's hot for two girls to make out.
These 'bisexuals' further contribute to the difficulties real bisexuals face and perpetuate the stereotypes that all bisexuals are attention seeking, slutty/whorish, and want multiple partners. This is simply not the case for most true bisexuals.
The best thing to do with a MySpace Bisexual is to ignore them. They are a special species of troll, and like all trolls, they will eventually leave your forum or site if they do not receive the attention they require to thrive.
There are not this many female bisexuals in the world - the numbers are currently artificially inflated by the scores of MySpace Bisexuals popping up everywhere.