4% report themselves as gay/lesbian while 19% as bisexual. I don't believe any of this. Is claiming to be bisexual a new fashion trend or something? Assuming it is a fashion trend, I don't understand where the trend came from; most 4chan users are male, men tend to be homophobic and if a man is bisexual then he also sleeps with other men. This doesn't make sense.
Looking at the age , it's quite normal that some of them feel like interested in experimenting. I have some friends that in our college years had bisexual relations and later decided for one side or the other, but if you ask them they tell you that in that time they felt bisex and only later took one side. I don't think it's strange, a lot of them are young people trying to find themselves.
In one of OK Cupids fascinating data reports, they showed that the vast majority of people who labelled themselves bi-sexual only contacted one gender.