15. Do social networks prevent us from creating meaningful “face to face” relationships?

Yes. The more you get into the world of communicating using social networking services, the more you start to lack in the confidence of interpersonal skills, leading you to have difficulties when communicating face to face. You could plan a hang out with a few cool friends you made through the social networking systems, but why bother go out of you're perfect world to communicate with someone else when you know you're poor talking face to face. Even if these people met, it would not be as "deep" as regular hangouts, where the people are not some random strangers from the internet.