The wide availability of user-provided content in online social media facilitates the aggregation of people around common interests, worldviews, and narratives. However, the World Wide Web (WWW) also allows for the rapid dissemination of unsubstantiated rumors and conspiracy theories that often elicit rapid, large, but naive social responses.

PDF here: http://www.pnas.org/content/113/3/554.full.pdf

via Proceedings of the National Academy of Sciences of the United States of America