I’m sure most of us are familiar with Craigslist, an online Web community where people post job opportunities, items for sale, and find activity partners. Over the past years, Craigslist has grown by leaps and bounds and now has Web sites representing over 300 U.S. cities. Many of us have used Craigslist to find a garage sale or buy a used couch.

However, despite its millions of users and various social benefits, there’s a dark side of Craigslist that most users don’t see. In the “Erotic” section, human traffickers have found Craigslist to be one of the most efficient, effective (and free) ways to post children and women for sale.

With a bit of research, one can realize just how much of a problem this has become. In one recent case, two Chicago women were charged for selling girls as young as 14 years old on Craigslist. The girls were forced to have sex with 10-12 men per day, and the traffickers made tens of thousands of dollars. A Boston man and his niece were charged with plotting a child trafficking operation with teenagers as young as 13 by selling them on Craigslist to predators from Massachusetts to New York. These cases are just the tip of the iceberg. In fact, law enforcement efforts to fight trafficking nationwide are consistently reporting a spike in online Craigslist ads, and how sex trafficking has “moved online” lately.

In Washington, DC, we see an average of 500 of these such Craigslist ads each new day. Yet, it is important to realize that a significant percentage of these ads on Craigslist do not advertise solely “legal escort services” as Craigslist may like to believe. Instead, a considerable percentage of the ads are a thinly veiled guise for one of the many faces of human trafficking that exists here in the United States. Although Craigslist may convince itself that it has created a beneficial online venue for advertising legal escorts, in effect, what it has done is create a fertile ground for traffickers to further their trade in human misery.

Many of the victims of human trafficking that Polaris Project has served have had their pictures posted on Craigslist. Through serving them, we’ve learned how the pictures on Craigslist hide the pain behind the smile. Maybe Craigslist should ask itself if the marginal benefits of this form of free advertising for the sex trade are worth the far larger human costs.