Nescafe Hungary, part of the Nestle food giant, apparently made that mistake. It ran a contest, inviting Hungarians to submit ideas for charitable projects, and promising they would be considered if they got at least 20 "likes" on Nescafe's Facebook page.
According to posts on the page, a young man named Janos Szolnoki got 47,000. He proposed that the prize money be used to help his disabled 11-year-old brother Milan -- but Nescafe Hungary disqualified him because he went on another website, 9gag.com, asking people to help him run up his vote count.
Szolnoki may have made a mistake -- but the company soon found it had made a bigger one. On Facebook and Twitter, users exploded in several languages.
The contest had been getting perhaps a hundred comments per Facebook post before the incident; when it tried to explain it got more than 4,000.
"NESCAFE BOYCOTT," screamed one. "COPY AND PASTE IN ALL NESCAFE POSTS."
"U Mad Nescafail?" said another.
"@Nescafe, if I were you, I would make a call to the Hungary company: you are going down veeery quickly," wrote a Twitter user named Ignacio Ruiz.
"Lessons in how NOT to do a social media campaign, by Nescafe Hungary," said another message that was retweeted from America to Australia.
Nescafe tried to explain the rules -- "The judging was based on a broad range of criteria, not based on the number of 'likes' received" -- but that only made things worse.
"If I were you, Nescafe," wrote a Facebook user named Toth Norbert, "I would think about the cause of this hate wave from the internet community instead of referring to the rules before you completely send your corporate image down the toilet."
Nescafe finally relented: "We have looked into this carefully and can confirm that the rules of the competition were followed fairly and we have been in direct contact with Janos Szolnoki and have been able to reassure him that no guidelines were broken." It finally said it would donate 1 million Hungarian forints (about $4,300 U.S.) to an institute that offers support for disabled children.
"You did right! From now on, we will drink Nescafe again!" was one of the 500 responses on Facebook.
Robin Grant, who heads a social media marketing agency in London, said the whole thing was a public relations disaster.
"On the face of it, it appears Nestle did nothing wrong, but still ended up facing the wrath of a significant portion of the Hungarian public," Grant said on a U.K. marketing website, The Drum. "It's clear that not only could Nestle have been clearer about the mechanics of the competition but also they also could have responded to the incident in a more timely and empathetic manner."