People who are happy, in general, buy more. Facebook has played with algorithms in the past to highlight happier news in an effort to get you to buy more (and engage more with the site). The origin of the “like” button may be innocent, but it’s continued presence is specifically designed to dissuade you from spreading bad news.
As a good example of this, during the period that Twitter was seeing the early Ferguson riots unfold in real time, Facebook feeds had such news conspicuously absent from the news feed. Fb’s top story at that time was the “Ice Bucket Challenge”.
Wiki may have a related bias. See Friendly WikiWikiWeb
Facebook may soon have a dislike button to better deal with death and protest. (html)
Twitter’s November 2015 switch from stars (favorites) to hearts (likes) is an example of this trend. See Lowest Common Denominator Twitter.
Source: Friendly Web