Raising awareness, gathering support and generating activity are the purposes of many public campaigns. There’s nothing new in this.
But the speed and international spread of the Facebook group Support the Monks’ protest in Burma does suggest a new departure. 90,000 supporters within a week and growing fast. (It’s a timely reminder after a few bad weeks in the press that Facebook users are not only interested in ephemera and ‘me me me’.)
Of course, joining a Facebook group is easy; doing something, sustaining a campaign and making a difference are harder tests.
PR Studies 
Well stated, Richard. Easy to join a club but much harder sustain your involvement. Much like I tell my students about joining IABC or CPRS.