The government does not want to study 'social pollution'. They want to study radicalizing propaganda from other nation states (and to a lesser degree from groups inside the United States) that seek destabilization.

"...it is imperative that we develop empirically-based procedures for countering messages that promote violent extremism and anti-Western beliefs..."

"...Neural predictors of Twitter impact in Cairo (UCLA & Egypt). Our prior work (Falk et al., 2012),
indicates that neural responses of a small group can predict which persuasive messages will be more
successful in mass media campaigns..."

"... Defense Group Inc. already tracks Twitter trends specific to Egypt and will identify which of the selected Twitter topics went on to be highly influential over the next month and which did not..." - Matthew Lieberman, UCLA, September 30, 2012, Department of Defense MINERVA Initiative [1]

The United States engages in targeted mass media and social manipulation to stir dissent in target nations, and to quell dissent where destabilization would hurt policy objectives.

Just this past year the CIA (under USAID) pretended to be a grassroots movement on Twitter and served 'news' critical of the Cuban regime for the purposes of, and that nearly caused, a Cuban uprising.

The DoD's MINERVA project specifically looks to understand the cultural components of stability of various countries and mechanisms to encourage or disrupt that stability. Among a great number of social studies you will find DoD research on how to seed information inside of specific Asian countries, including China, for the targeted introduction of instability. I will leave speculations of possible connections to the Hong Kong protests to the reader. [2]

This should not come as a surprise given the history of the US: The United States and allies are known to target media in other countries to stir dissent. Radio Free Europe, "Voice of Iraq" (cough American), the Lincoln Group infiltrations and partnerships, etc.

But now with global interconnectedness it is easy to set up 'foreign media', blogs and other politicizing content to influence other nations' populations.

In the past decade it has become a global issue.

This year Egypt sentenced Al Jazeera journalists that they believed were partnered with geopolitical interests of other states.

Putin's administration is now requiring bloggers to register if they have a certain number of readers, so that his administration can curtail international influence.

China blocks many American services including Facebook and Google. The usual story in America is that they are censoring free speech. The truth is that they do not want foreign influence to destabilize their population and that they do not want their citizen's data in America's PRISM program (there's a reason it's called the FISA "Foreign Intelligence Surveillance Act" court).

The Snowden revelations showed us how intelligence agencies are involved in PsyOps - the term for 'psychological operations' used by the CIA and others.

The GCHQ's BIRDSONG/BADGER/GATEWAY/SLIPSTREAM/ETC and partnership with the NSA are used to influence online polls, discussion forums and to vote up and down content that aligns with policy goals. [3][4][5]

The giant meta-data graph created by the NSA is also particularly valuable for 'influencer' and 'social contagion' analysis (leaks showed they do use it to understand internal chain-of-command and organization structure for target selection). It's why metadata matters. A nice illustration of this is the article "Finding Paul Revere."

And so we have issues here with the use of targeted social influence in America as well.

A number of journalists have called out that the state has been extremely aggressive to dissenting opinions, even to go so far as labeling current policy on the issue "War on Journalism". American officials have exported a number of journalists with Middle Eastern descent and journalists like Ayman Mohyeldin have been pulled from Gaza and other conflicts when reporting has erred on the side of other state interests. The crackdown on journalism is worth another post I don't have time to write.

And of course there's the article "I Liked Everything I Saw on Facebook for Two Days", which is definitely worth a read. Below the thin surface of social information bubbles enormous amounts of radicalizing geopolitical and domestic political ads and campaigns. [6]

"Here we report results from a randomized controlled trial of political mobilization messages delivered to 61 million Facebook users during the 2010 US congressional elections. The results show that the messages directly influenced self-expression, information seeking, and real world voting behavior of millions of people. Furthermore the messages not only influenced the users who received them but also the users' friends, and friends of friends." - Robert M. Bond, Christopher J. Fariss, Jason J. Jones, Adam D. I. Kramer, Cameron Marlow, Jaime E. Settle & James H. Fowler [7]

[1] http://minerva.dtic.mil/doc/samplewp-Lieberman.pdf

[2] http://minerva.dtic.mil/funded.html

[3] https://firstlook.org/theintercept/2014/02/24/jtrig-manipula...

[4] http://www.theguardian.com/commentisfree/cifamerica/2011/jun...

[5] http://www.dailykos.com/story/2011/02/16/945768/-UPDATED-The...

[6] http://www.wired.com/2014/08/i-liked-everything-i-saw-on-fac...

[7] http://jhfowler.ucsd.edu/massive_turnout.pdf