Facebook's Response to Critisism Over Secret Manipulation of Users

Facebook has defended itself against a sharp criticism over an psychological experiment  it conducted to manipulate user moods by altering amount of positive or negative content appearing of News Feed. Their defense was that the experiment was meant to "“improve our service and to make the content people see on Facebook as relevant and engaging as possible.”
However technologists and lawyers have expressed fear that the same method could be used to manipulate users for political gain ,academicians on their part have criticized Facebook for failing to acquire the consent necessary   for subjects of human experiment.
A Facebook Spokesperson  said relieved that research was conducted for a single week in 2012 but none of the data used was associated with a specific person's Facebook account.
" We carefully consider what research we do and have a strong internal review process. There is no unnecessary collection of people’s data in connection with these research initiatives and all data is stored securely.”   he added.
Some 689,000 users were drafted into the experiment which manipulated a "small percentage" of content. The study concluded that: "Emotions expressed by friends, via online social networks, influence our own moods, constituting, to our knowledge, the first experimental evidence for massive-scale emotional contagion via social networks."
Fears have been raised of Social Networks manipulating people emotions on political and other areas using material from their personal lives.
This experiment is particularly  disturbing following the revelations of Edward Snowden that the US plot to create a Cuba Twitter to causes unrest in Cuba