"These estimates are based on an internal review of a limited sample of accounts and we apply significant judgment in making this determination As such, our estimation of duplicate or false accounts may not accurately represent the actual number of such accounts," it said.

The figures may not do Facebook any favours with its advertisers today, but better reporting will likely be for the best in the long run.

"Companies who are considering advertising on the social network want to be sure that any 'likes' they receive are from genuine users, not bogus accounts," said Graham Cluley, senior technology consultant at Sophos.