Facebook has begun a long-awaited cull of fake users and profiles, after it was revealed up to 80 million people on the site didn't exist.

Beginning on Wednesday, the action saw tens of thousands of accounts deleted.

Some of Facebook's most popular pages saw their fan counts drop by as much as 100,000 following the cull.

Zynga's Texas HoldEm Poker game lost more than 96,000 fans, while Justin Bieber, South Park, Eminem and Rihanna all register five-digit drops, according to Techcrunch.

The move is intended to make Facebook a more attractive place for advertisers, by making it easier to target advertising at genuine users.

The large amount of fake users on the site - estimated by the company to be about 8.7% of all accounts - sent Facebook's shares below $20 for the first time in August.

The 8.7% figure was up from an estimated 6% in March 2012, due to a change in accounting.

That should start to drop as Facebook continues the cull - though it has stopped a controversial move in which it asked users to report their friends who were using parody, fake or misnamed accounts.

In August Facebook said:

"These newly improved automated efforts will remove those Likes gained by malware, compromised accounts, deceived users, or purchased bulk Likes. While we have always had dedicated protections against each of these threats on Facebook, these improved systems have been specifically configured to identify and take action against suspicious Likes."