From BBC News (by way of Marginal Revolution):
Dating by blood type in Japan
The black sheep though seem to be blood group B – flamboyant free-thinkers, but selfish.
“At the interview for my first job they asked me about my blood type,” said a man with blood group B, who wanted to identify himself only as Kouichi.
“The surprise was written on my face. Why? It turned out the company president really cared. She’d obviously had a bad experience with a B type blood person. But somehow I got the job anyway.”
Later, though, the issue of his blood came up again.
“The president was the kind of person who couldn’t take her drink and at one company party she got drunk. So she sent B people home before the others. ‘You are blood type B,’ she said. ‘Get out.’”
There is even a term for such behaviour in Japan, burahara, which translates as blood group harassment.