It is not just politicians who have cause to complain about fake news.
Starbucks fell victim to fakery this month when tweets advertising "Dreamer Day", in which the coffee chain would supposedly give out free frappuccinos to undocumented migrants in the US, spread at lightning speed online.
Advertisements including the company's logo, signature font and pictures of its drinks were circulated with the hashtag "#borderfreecoffee". But it was dreamt up by a hoaxer.
"How about we meme 'Undocumented Immigrant Day' at Starbucks into existence?" one user of the messaging board 4Chan had asked on August 2. "Could cripple their business a bit."
Starbucks raced to deny the event, replying to individuals on Twitter that it was "completely false" and that people had been "completely misinformed".
Yet the rapid spread of the fake news showed again the power of social platforms to damage reputations, and illustrated how companies are having to be more vigilant and creative in responding.
Snopes, the factchecker, compiles a top 50 of "hot" fake news stories, and in a recent week 12 were about companies.
The 4Chan user who faked the Starbucks news was politically motivated: he wrote that he was searching for a "liberal place" and said that if illegal immigrants gathered there, he would call the US Immigration and Customs Enforcement.
Other companies have also been targeted by suspected Trump supporters, such as with the false story that Indra Nooyi, Pepsi chief executive, told the president's supporters to "take their business elsewhere".
Much fake news is not motivated by politics, however, but by the hope of generating advertising revenue — or just attention-seeking.
Brooke Binkowski, managing editor of Snopes, says: "It hurts businesses financially and it also makes things toxic for them by destroying trust and creating an atmosphere in which people don't know who they can trust. It is the same tactics that were levelled on us as a country, really."
Companies have long had to deal with news stories that claim a "particular brand of soda causes cancer", says Mandy Jenkins, head of news at Storyful, a social news site.
But now the problems of a disgruntled customer or employee can become twisted as they are broadcast to the world.
"A few years ago, you would never imagine this was something you had to deal with," she says.
"Maybe you would get a letter from a person. Now, millions of people know about the incident because maybe someone had a bad day working in McDonald's in Kansas."
The major internet companies have introduced measures to try to slow the spread of misinformation this year. Facebook and Google have tried to cut fake news sites off from their advertising platforms, so they cannot make money.
Facebook has partnered with fact-checkers such as Snopes so that users can flag any news they suspect is fake.
If it is declared false by the fact-checkers, it is tagged as "disputed" and its ranking in the news feed is lowered. Twitter has systems for reporting accounts that attempt to impersonate a brand.
But the platforms have not created special avenues for companies to report fake news before it potentially affects a share price or sales.
PR and crisis management teams are relying on other services: Storyful now has an arm that provides business intelligence on what is being said on social media, and PR firm Weber Shandwick is marketing crisis simulation software called Firebell to prepare companies for being caught in a social media firestorm, whether it is a fake story or a presidential tweet.
Leslie Gaines-Ross, Weber Shandwick's chief reputation strategist, says companies are now realising how vigilant they must be, recruiting every employee to be their eyes and ears on social media.
Monsanto has been dealing with rumours about its genetically modified crops for years. It learnt it needed to switch its focus from engaging with farmers and investors to looking at the broader internet.
Vance Crowe, Monsanto's director of millennial engagement, says he tries to stop rumours at their origin, spending time "hanging out" online with different "tribes".
"The agricultural tribe is really heavily on Twitter, they are sitting in combines and planters and listening to podcasts. Sceptics spend a lot of time on sites like Reddit and have their own YouTube channels," he said.
He does not combat the reports directly but tries to connect with "the underlying values of this tribe".
What is shared on social media is an expression of group loyalty, he said. "If you shoot at it, people don't view that as you shooting at their idea, they view that as you shooting at their friend," he said.
Monsanto's tactics were tested when a fake news story on WorldTruth.TV claimed that its pesticides were responsible for the microcephaly cases in Brazil, not the Zika virus.
Mr Crowe said Monsanto encouraged its employees to use social media and, declaring they worked for Monsanto, represent their case to friends and contacts.
The company believes that their message was distributed as effectively, if not more so, as anything that came from the company directly and it became a "point of pride" for employees, Mr Crowe said — a small win in the battle against fake news.
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