I actually think it is because BB has neglected them and their intellectual (most of them, bear with me) needs and they are bored out of their brains. When BB sent in ex-housemates for the birthday task, and some said about how badly BB are neglecting them with treats etc., that was when the rebellious seed was planted. If BB had entertained, stimulated, or at lead had better tasks this may not have happened. BB eats itself in a natural evolution of the show's decline, but I agree, Yay for the rebels!
