Hi I can tell you about LaComune Di Milano page on Facebook. This is not a media, but something like. It's actually a subvertising media. making political information on the streets with signs that mimic the official signs of the municipality of Milano, Italy. If you do not understand italian, you can have some informations here http://www.memefest.org/en/profile/lacomune/ (La comune is patricipating to Memefest festival)
As you can see LaComune has around 1 thousands friends. In the first steps they came just a while after each action (the first 300). Then people starting asking friendship just because they have seen the profile in their friends page. They were probably curious about the odd icon. The power of Facebook as we know, is to let people spread your news sharing the post with others . And feed many comments all over.
Now there is some people who download the signs, print them and put them on the streets. And even if there is also a website (http://scusateci.noblogs.org) facebook is far more useful to spread the news of new actions.
La comune has also a Twitter, but probably this could be more useful if the action were made very often, which of course is not.
I hope this can be useful for you