teaching internet safety to an 11 year old

While I was home for Thanksgiving my sister was begging my mom to let her get a facebook. My mom has decided that she's too young and that it's dangerous to let her put that kind of information online. She was really put out and thought my mom was being unreasonable. So I sat her down and talked with her about the kinds of things people put online that can be dangerous. I signed on to my facebook account and started looking up some of her friends who have facebooks. I told her to try to see if she could tell from the information on their page which school her friends went to or how old they were or where they lived. We found pictures of her friends in their elementary school t-shirts and even found a girl who had posted her phone number in her status. I actually know the older brother of one friend who had way too much personal info on her page and I told him that to help her figure out how to change her privacy settings. After doing that she realized a lot more how easy it is to post personal information online and how she really isn't old enough. (Especially because facebook requires you to be 13, so she'd have to lie about her age.) She's still not very happy about it, because apparently facebook is the it thing for her group of friends right now, but she gets that my mom isn't just being strict for no reason.