A woman shoots a video of the sign at the entrance to the Facebook main campus. AFP/Robyn Beck
The site said that leaving a comment on a story within Facebook also adds to the tally, the BBC reports.
"Many websites that use Facebook's 'like' or 'recommend' buttons also carry a counter next to them. This counter reflects the number of times people have clicked those buttons and also the number of times people have shared that page's link on Facebook, the site explained.
"When the count is increased via page shares, no user information is exchanged. 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 on fix to solve the issue now," it added.