The comparison that some have made between the US Government and Stasi is more accurate than you think, with regards of Zersetzung:
> By the 1970s, the Stasi had decided that methods of overt persecution which had been employed up to that time, such as arrest and torture, were too crude and obvious. It was realised that psychological harassment was far less likely to be recognised for what it was, so its victims, and their supporters, were less likely to be provoked into active resistance, given that they would often not be aware of the source of their problems, or even its exact nature. Zersetzung was designed to side-track and "switch off" perceived enemies so that they would lose the will to continue any "inappropriate" activities.
Source: http://en.wikipedia.org/wiki/Stasi#Zersetzung
Data mining is a very interest challenge and represents a major step in large-scale computing technology, but it pales in comparison to data manipulation.
Imagine for a moment if the intelligence-surveillance apparatus were redirected outward: methods used for parsing human communication would be re-purposed for disseminating seemingly-human propaganda. Who you're responding to on Twitter, reddit, or HN may not be a person.
Imagine for a moment if spammers were quite a bit more convincing in their emails, and that their poor grammar and spelling were improved.