Mary Beth Hertz (@mbteach on Twitter) is an elementary computer teacher in Philadelphia, PA and a regular blogger on Edutopia. You can read more of her work on her own blog at Philly-teacher.
With children spending time online at younger and younger ages, it is vital that we explicitly teach young children how to protect themselves online. Most young children get the "Stranger Danger" talk at school, so they know about how to handle strangers in their neighborhood and in face-to-face situations.
Gust MEES: check out also my courses and ideas on How-To IT-Security could get taught to kids and also adults: they are in French, use translation tools please...