Mandell said studies show that parents who talk to their kids — about the Internet or anything else — have more of an impact than you might think.

"They may appear to not be listening, but they are," he said. "People who have studied child and adolescent behavior have seen lots of evidence over a span of decades that not only do children listen to their parents, but most of the time they are listening pretty closely. They know exactly what your standards are, and if you have a healthy relationship, they incorporate those standards and internalize the values being taught."

Both Cooper and Mandell added a few caveats. Mandell said parents are justified in investigating what teens are up to if there is evidence of substance abuse or other signs of trouble — inappropriate relationships, a plunge in grades, or a psychiatric or developmental disorder.

Cooper added to the list of warning signs unsolicited gifts from strangers and mysterious long-distance phone calls.

Cooper also said parents should supervise younger children more closely than teens, including setting password-protected parental controls that allow you to block objectionable content, and letting them know you'll be checking the Internet history to see what Web sites they're visiting. He did that when his two children were younger.

But does Cooper spy now that his kids are teenagers?

"I don't," he said, adding that he thinks his teens are mature enough to understand the risks and make the right decisions.

That's a philosophy Mandell approves of. "There's no reason to track every movement your kids are making unless you haven't built up the sense of trust and healthy flow between parent and child that takes years to achieve," he said.

Mandell said digital spying not only undermines trust, but kids can outsmart us by deleting incriminating messages, making calls from friends' phones and disabling software.

"Of course they can beat you at that game," he said. "They're more technologically savvy than we are."

As for me, my son still won't friend me on Facebook.

But that's OK. I found lots of mom friends on the site. They'd all been rejected by their kids, too.

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Beth J. Harpaz is author of several books, including "13 Is the New 18."