  This paper explores the growth of online mobilizations using data from the
'indignados' (the 'outraged') movement in Spain, which emerged under the
influence of the revolution in Egypt and as a precursor to the global Occupy
mobilizations. The data tracks Twitter activity around the protests that took
place in May 2011, which led to the formation of camp sites in dozens of cities
all over the country and massive daily demonstrations during the week prior to
the elections of May 22. We reconstruct the network of tens of thousands of
users, and monitor their message activity for a month (25 April 2011 to 25 May
2011). Using both the structure of the network and levels of activity in
message exchange, we identify four types of users and we analyze their role in
the growth of the protest. Drawing from theories of online collective action
and research on information diffusion in networks the paper centers on the
following questions: How does protest information spread in online networks?
How do different actors contribute to that diffusion? How do mainstream media
interact with new media? Do they help amplify protest messages? And what is the
role of less popular but far more frequent users in the growth of online
mobilizations? This paper aims to inform the theoretical debate on whether
digital technologies are changing the logic of collective action, and provide
evidence of how new media facilitates the coordination of offline
mobilizations.
