Demonstrations

An example of political activism in social media can be people who use the internet to spread a message about a demonstration or something like that. 

Here is an example in Spain where some young students made a demonstration because of the politics and crisis. The students spread the news about the demonstration somewhere on the internet. Because of the news on the internet the amount of people attending the demonstration became bigger, and bigger. 
An example of one of the internet sites:
http://www.facebook.com/Mov15M

Another example is a worldwide demonstration against the movie: KONY 2012. 
http://www.facebook.com/events/371156052914638/ 
Events like this were set up in almost every country, to make as many as possible demonstrate.