John Key was kidnapped in Peru by drug lords along with other heads of state and is held hostage in a mountainous area". If you saw that message on social media, you might just think it's true, especially if it was accompanied by a link.
Key's in Peru, a country that produces large amounts of cocaine with violent drug lords running that business.
As it seems plausible, you share the message with friends and others, it goes back and forth on social media and some people give it the benefit of doubt.
Thanks to the power and reach of social media, in a short amount of time, maybe thousands of people have seen the message with some of them taking action based on what it says, like dumping their shares or cancelling business transactions before the false news is wound back.
Call it fake news, post-truth or trolls that got Donald Trump elected, the amount of disinformation on the internet is becoming dangerous, and weaponised.