Why do we love goss… but hate a gossip?

When someone says "I've got goss" we get a visceral reaction, it brings out the best and the worst in us. So why is it that we absolutely cannot resist the goss? We have an insatiable appetite to hear about the private lives of celebs – people we'll probably never meet in real life… but beyond providing good banter about who is sleeping with who does gossip have a role to play in keeping society running smoothly?