How useful is SOR?

A local paper has this,

Law enforcement officials and researchers caution that the registries play a limited role in preventing child sexual abuse and stress that most perpetrators are known to the child. The U.S. Department of Justice, which oversees the National Sex Offender Public Website, estimates that only about 10 percent of perpetrators of child sexual abuse are strangers to the child. The Justice Department estimates 60 percent of perpetrators are known to the child but are not family members but rather family friends, babysitters, child care providers and others, and 30 percent of child victims are abused by family members. Nearly a quarter of the abusers are under the age of 18, the department estimates.