Hayden, Thomas (2005) Why we need the nosy Parkers
U.S.NEWS & WORLD REPORT, 6/13, 74.

Busy bodies are the glue of society. They gossip and verbally punish the mildest rule breaker without much reward. However, they are needed. As unfortunate as they are to be around, they have a function and every group has one.

Humans regularly cooperate with complete strangers, even when there is no expectation for the reward.