I think it's two things: the power of malice, and popularity measurement. Malice and fame. Social networks are devices for measuring popularity; if you took t

I think it's two things: the power of malice, and popularity measurement. Malice and fame. Social networks are devices for measuring popularity; if you took the up/down arrows off, no one would be interested in playing. And we have proven once again that nothing gets up arrows like being mean. HN has the unusual property that you can't (readily) see others' score, just your own. That doesn't really make it any less about fame, but maybe it helps. When advertising can fund these devices to scale to billions, it's tough to be optimistic about how it reflects human nature.