Earlier, I introduced the problem that troubled teens can make social media friends who are a way bigger problem than their parents.
Parents can be misguided about what is good for their children but usually they want what is good, in principle. And in most communities, the resulting conflicts iron themselves out over time.
Strangers may not be so particular about what is good for the kid. So how can we help kids understand the risks of trusting interesting strangers (instead of the boring, oppressive ordinary folk one lives with in everyday life)? Here's a site that offers to help us snoop on kids. (More than a monitoring service, uKnowKids is Parental Intelligence. We help you understand your child’s digital footprint so you can focus on what you do best – parenting.)

Real-time analysis of your child’s social and mobile activities in an easy-to-use online or mobile dashboard. Plus educational resources on the latest trends impacting your family.

Stay connected with how your child communicates on his or her phone. Review text messages, call history, apps, and photos on your child’s Android. See photos and contacts on an iPhone.

If you provide log-in credentials, we can help you make better sense of who your child is connecting with and how they are interacting on Facebook, Twitter, and Instagram.

And so forth.
There are probably kids who need this.
Indeed, it isn’t just kids. I am no stranger to the problem of confused seniors who need monitoring, though it is rarely about online issues.
More likely, in the case of seniors with cognitive issues, they can wander into a blizzard in order to reach a home they no longer own, a farm that is now a subdivision, or people who died thirty or even sixty years ago.
From that background, I don’t have a problem with monitoring in principle, provided it improves safety, health, and lifestyle. But because I have dealt with the problem from both ends (the teen and the very elderly), I suggest a somewhat different approach for the teen. Maybe I can break it into three parts:
1. Teens should be taught to act for their own safety. Disagreements with parents about curfews, friends, etc., should never be a reason to trust a stranger, met online or anywhere else. Families tend to stick together or come back together over decades, whether they like each other or not. A stranger may, knowingly or otherwise, be looking for an alienated teen to exploit and then dump. Make sure the teen can always come home instead, no matter what happened with other contacts. 2. Teach critical thinking, but mainly by example. We should demonstrate it by our own prudence.
Critical thinking isn’t cynicism; it just means awareness of the components of a given person’s point of view. Of course the coach thinks that her volleyball team is the best; that’s her job! It doesn’t mean that a teen player should delude herself that an online stranger who claims she is Olympic material, is an impartial witness. He could be trying to meet her for inappropriate or even dangerous reasons.
3. I always end with this theme, with respect to the Internet: If it sounds unbelievable, don’t believe it. And when in doubt, doubt.
Here’s an explanation of the Uknowkids system:
 

Denyse O’Leary is a Canadian journalist, author, and blogger.