Overall, almost 20,000 people made approaches to the virtual girl -- who was modeled on a 10-year-old -- but the charity was unable to track them all down.
"The child predators doing this now feel that the law doesn't apply to them," said Hans Guyt, director of campaigns at Terre des Hommes Netherlands. "The Internet is free, but not lawless."
He added that real children were often forced into remote commercial child sexual exploitation -- or "webcam child sex tourism" -- by adults or extreme poverty.
"Sometimes they have to testify against their own family, which is almost an impossible thing to do for a child," Guyt added. "Once a child has become a victim of sexual abuse, rehabilitation can take many years. It is along, painful, and labor-intensive process for children to overcome the trauma."
Using methods similar to Dateline NBC's "To Catch a Predator," the researchers worked from a building in Amsterdam during the summer. "Sweetie" was placed in public Internet chat rooms and the charity's investigators waited for her to be approached.
"Sweetie" was deluged with requests for sexual webcam performances and while the would-be predators interacted with the virtual girl, researchers gathered information about their identities.
Image: "Sweetie," via http://www.terredeshommes.org