Facebook is working to fix a "bug" which apparently allowed users to inflate the number of 'Likes' on a page.
A video posted to YouTube, since taken down, appeared to show that two 'Likes' would be added to a page if a user emailed a link to a friend using Facebook's Private Message service.
Up to 1,800 Likes an hour could be generated using this method.
Leaving a comment on a story within Facebook also added a 'Like' to the page, a BBC report said.
The news led to concerns in Wired and other publications that Facebook was mining the data in a user's private messages.
But Facebook said in a statement that no private information had been shared, and denied that it was automatically Liking pages on a user's behalf.
"We did recently find a bug with our social plug-ins where at times the count for the Share or Like goes up by two, and we are working to resolve the issue now," Facebook told the BBC.
The site explained that the numbers that are affected are the counters on websites using Facebook sharing plugins.
The counters mark how often a page was 'shared', which Facebook says are not the same as liking a page within the social network itself.
But reports pointed out the distinction would be unclear to many - and that in some instances campaigners sharing links to highlight negative content would actually be boosting the page's popularity.
The news comes as the social network celebrated signing up its billionth member on Thursday.
Writing on his own Facebook page, CEO Mark Zuckerberg said:
This morning, there are more than one billion people using Facebook actively each month. If you're reading this: thank you for giving me and my little team the honor of serving you.
Helping a billion people connect is amazing, humbling and by far the thing I am most proud of in my life.
I am committed to working every day to make Facebook better for you, and hopefully together one day we will be able to connect the rest of the world too.
In a press release, Facebook said that since its launch it had also racked up:
- 1.13 trillion Likes
- 140.3 billion friend connections
- 219 billion photos shared
- 17 billion check-ins
- 62.6 million songs have been played 22 billion times that's about 210,000 years of music
- 2.45 billion content items and 2.7 billion Likes are shared every day on Facebook.
- More than 300 million photos uploaded daily.