Well, from the article you cited: >Mr. Kramer wrote that changing the emotional makeup of the news feeds had a minimal impact, prompting users to produce an av

Well, from the article you cited: >Mr. Kramer wrote that changing the emotional makeup of the news feeds had a minimal impact, prompting users to produce an average of one fewer emotional word per thousand words over the following week. What I am saying is that I find unlikely that they can change the voting preference, if not that of really gullible (or if you prefer "very easy to manipulate") people.