Word out today that Facebook has as many as 50 million fake or duplicate Facebook accounts on their network.

An updated IPO filing today, the company said it estimates that 5% to 6% of all their accounts are false or duplicate. That means that between 42 million to 50 million Facebook accounts aren’t real.

In the filing, Facebook said their estimate may not be accurate. They wrote: “We estimate that false or duplicate accounts may have represented approximately 5-6% of our MAUs as of December 31, 2011. However, this estimate is based on an internal review of a limited sample of accounts and we apply significant judgment in making this determination, such as identifying names that appear to be fake or other behavior that appears inauthentic to the reviewers. As such, our estimation of false or duplicate accounts may not accurately represent the actual number of such accounts.”

The social networking company did not say how many accounts they have shut down for being fake.

So how would all the fake accounts come about? Well, some are simply spammers or scammers, out to promote their latest offering. A good number of them are also set up by companies who sell ‘Likes’ and/or ‘Friends’, so that companies can pad their numbers and look popular.

As an example, Newt Gingrich’s campaign had 1.3 million followers back in August of 2010. But when a study was done by a group at Indiana University, they found that nearly 80% of those followers didn’t have a profile/bio on their account. While it’s possible for a real user not to have a profile, it’s not in the 80% range.

There are services available online in which companies can buy thousands of ‘likes’ or ‘followers’ at a time. The same thing happens with other social networks, including Twitter.