Marketers use social media sites likeFacebook and such to target and gather info about the teen market. Cool if you’re selling a product to that audience. Not so cool if you are a parent of a teen and are wary about him or her giving away too much personal data and risking privacy, safety and security.Teens under the age of 13, technically aren’t even allowed on the site per Facebook’s Terms of Service, yet parents buckle to pressure from their kids or let them on for the limited purposes of playing Facebook app games. The thing is, after they’re on, they are less likely to be aware of giving away their privacy.Stanford computer science professor Monica Lam, who created the social chat app, Omlet [www.omlet.me], has identified four ways that teens give away their privacy and empower teen marketers without even knowing it: 1.  GIVING UP RIGHTS TO PERSONAL CONTENT

Facebook actually “owns” any family photos, messages, and unique ideas that you create and post on the site or via its app.2.  EMPOWERING MARKETERS BY “LIKING” THINGS

With its “likes” functionality, Facebook allows marketers to target you based on the people and things you associate with yourself.  Every time you like something, you are giving a bit of privacy away.3.  SHARING INFORMATION ABOUT FRIENDS

By using Facebook to login to other websites, you’re unknowingly sharing much of your friends’ private and valuable data with third parties (and your friends could be sharing your data, too).4.  TAKING QUIZZES THAT STORE PERSONAL PREFERENCES

Any time you take a Facebook quiz, you’re potentially making public a little bit more about yourself and your personal tendencies.Parents, be aware and take active steps to inform your teens and monitor their online activities.