Facebook’s share price dipped below $20 on Thursday after reporting slowing growth and an admission of an alarming number of fake accounts.
It also reported that as many as five percent of its active users have duplicate accounts.
Facebook members grew to 955 million this year.
It says 1.5 percent of its accounts are likely spam or accounts set up for other malicious activity.
The fake accounts are concentrated in developing markets, according to the filing.
It also blames people who set up accounts for non-human entities, such as pets.
There are “inherent challenges” in measuring usage,” the social network said.
“We are continually seeking to improve our ability to identify duplicate or false accounts and estimate the total number of such accounts, and such estimates may be affected by improvements or changes in our methodology,” the filing continued.
The number of real users is important for Facebook as it seeks to sell advertising.
Facebook shares are down almost 50 percent from its $38 May IPO.