Social network is very important to establish your life and career that can make your happy.

they are really good, they help me keep in touch with people and events happening in their life, and they also allow me to express myself.

There ok. 

It`s a good tool to know people, to learn languages, to meet new people. But It could be dangerous for the security and social life of some people.

For me social networks are a good place to learn a language. I sometimes use twitter to practice my Spanish.