Pizzagate
Not all conspiracy theories are benign, of course. After her loss to Donald Trump in the US presidential election, Hillary Clinton decried what she called the "epidemic" of fake news in the lead-up to the vote.
In an apparent reference to a conspiracy theory known as "Pizzagate", Clinton warned that fraudulent stories online had "real world consequences" and were putting "lives at risk".
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The Pizzagate conspiracy theory originally began to circulate on the anonymous message boards of image-sharing site 4chan.
It stemmed back to the WikiLeaks release of emails hacked from the account of Clinton aide John Podesta, in which there were references to James Alefantis, the owner of Washington DC pizza restaurant Comet Ping Pong and a Democrat fundraiser.
After finding pictures of children on Alefantis's social media accounts, conspiracy theorists concluded top members of the Democrat Party had turned the basement of his pizzeria into a dungeon and it was ground zero for a massive child sex-trafficking operation involving prominent politicians and political donors.
"We don't even have a basement," Alefantis told the BBC. "Sometimes an innocent picture of a child in a basket is just an innocent picture of a child in a basket and not proof of a child-sex trafficking ring."
However, the theory turned nasty in December when Edgar Welch, 28, from North Carolina, travelled to Comet Ping Pong, 250 miles from his registered home address, and allegedly threatened an employee and fired an assault rifle into the floor, NBC reports.
Welch told the New York Times he had only intended to give the restaurant a "closer look" and regretted how he handled the situation. "The intel on this wasn't 100 per cent," he said.