Effects of Social Networks

Social networks are becoming more popular nowadays. Then, for many people it's going to be their need. In fact, the users of  social networks such as Twitter and facebook is increasing, especially in my beloved country ( Indonesia ).... believe it or not... According to many sites and webs, indonesia is one of the countries which has the greatest amount of social networks users in the world...sounds great.. but still, there's a bad news..yah of course, we've heard about the crime that started from using this kind of social networks..
So, actually what is the effect of using social networks? of course there are so many effects, both positive or negative.. so, I'm going to tell you a little bit about that...