This isn't new, just the next step in what has already been done. But it's disturbing nonetheless and not just because it's Democrats who are utilizing this most effectively, although that's pretty disturbing too. But I don't know much comfort level is much higher with conservatives using this.
But the reality is we've made this possible by being part of social networks that provide the data to be mined in this fashion. Samuel Morse's first telegraphic message was: "What hath God wrought?" Morse may or may not have used that biblical verse to wonder what the invention of the telegraph might mean to mankind. One thing it definitely means: Morse never imagined the internet.