There are a growing number of reasons why more marketers these days are referring to the largest social media platform as “Fakebook.”

Back last year, it came to light that Facebook’s video view volumes were being significantly overstated – and the outcry was big enough that the famously tightly controlled social platform finally agreed to submit its metrics reporting to outside oversight.

To be sure, that decision was “helped along” by certain big brands threatening to significantly cut back their Facebook advertising or cease it altogether.

Now comes another interesting wrinkle. According to Facebook’s statistics, the social network claims it can reach millions of Americans across several important age demographics, as follows:

• 18-24 year-olds: ~41 million people
• 25-34 year-olds: ~60 million people
• 35-49 year-olds: ~61 million people

There’s one slight problem with these stats:  U.S. Census Bureau data indicates that the total number of people living in the United States falling in the 18-49 age grouping is 137 million.

That’s a substantially lower figure than the 162 million people counted by Facebook – 25 million (18%) smaller, to be precise.

What could be the reason(s) for the overcount? As reported by Business Insider journalist Alex Heath, a Facebook spokesperson has attributed the “over-counting” to foreign tourists engaging with Facebook’s platform while they’re in the United States.

That seems like a pretty lame explanation – particularly since U.S. tourism outside the country is a reciprocal activity that likely cancels out foreign tourism.

There’s also the fact that there are multiple Facebook accounts maintained by some people. But it stretches credulity to think that multiple accounts explain more than a small portion of the differential.

Facebook rightly points out that its audience reach stats are designed to estimate how many people in a given geographic area are eligible to see an ad that a business might choose to run, and that this projected reach has no bearing on the actual delivery and billing of ads in a campaign.

In other words, the advertising would be reaching “real” people in any case.

Still, such discrepancies aren’t good to have in an environment where many marketers already believe that social media advertising promises more than it actually delivers.  After all, “reality check” information like this is just a click away in cyberspace …