The excellent reply I know that most of the problems people encounter with privacy on the web are coming from their ignorance. I'm an elementary school teacher and we teach kids about dangers of Internet and trolls, but that is mostly inefficient. If people are more educated about those problems they would behave in a way that could prevent abuse of their integrity, but seeing how people expose their privacy on the social network is almost astonishing. People almost always learn the hard way. It's like playing with fire. When you get burnt its hard to heal up and it's easy to blame others.
Trolls, on the other hand, are people with their deep problems that can't deal with themselves for whatever reasons and we need compassion even for them.