Geotags embedded in pictures, which are later posted online, can reveal your (or your child's) location. Disabling the geotag feature can be a pain, but the information is very easy to retrieve for anyone who's got a mind to do so -- one more reason to lock down your Facebook photos, and make sure your kids are doing the same.
Facebook's new "Places" app reveals your location in your status updates, and you can tag a friend who's with you -- even if that friend doesn't have an iPhone. Again, disabling the feature is a pain, but it's crucial if you don't want others to reveal your child's whereabouts. Here's a step-by-step from Lifehacker.