Social media is, it seems, good for only one political thing, which is diffusing viral actionable campaigns against novel topics that are likely to instantly inflame the indignation of relatively young users. The viral spreading of the Kony video was one example. The campaigns against SOPA and PIPA, the two copyright protection bills are another. These two bills have been obstructed in the U.S. Government houses largely due to public pressure that has built through social media and demonstrated through masses of people acting on instructions to black out web pages and avatars and to call their representatives.
So if you want to do something political on social media, make sure to make it 1) meaningful to youth; 2) both novel and temporally relevant; 3) actionable.