In the infographic from below, created by Open Site, you can see that the idea that social media is the new major media is coined. Thus, social media is reactive. I’m not sure about it being a major media, however social media promises to be the big boy of the web and it has already proven it’s effectiveness in the Arab Spring Revolution.
Social media is also proactive. See the anti-SOPA/ACTA movement. The web has proven that can help in many ways and that we should not ignore any trends that can be seen. Sometimes you can read about an earthquake with 30 seconds before it hits you. Now, that is something!