I've made a big effort over a long period of time, starting early, to make sure that my kids know that people lie, on and off the internet. That random strangers appropaching them online or in person should be considered with a healthy level of suspicion, and that people lie to you in order to trick you into giving them something you wouldn't otherwise want to give. Often, that's money (or something of monetary value), but it could be sexual, it could be getting you to commit a crime on their behalf (or taking responsibility for a crime you didn't commit), it could be your vote, it could be simply to exercise power over you.
People lie, and it is a disservice to avoid that fact.