Obama’s campaign began the election year confident it knew the name of every one of the 69,456,897 Americans whose votes had put him in the White House. They may have cast those votes by secret ballot, but Obama’s analysts could look at the Democrats’ vote totals in each precinct and identify the people most likely to have backed him.

The Definitive Story of How President Obama Mined Voter Data to Win A Second Term | MIT Technology Review

So much for the secret ballot. We now shed so much data in the wake of our everyday digital lives that the most intimate aspects of our political lives–much less our intimate ones–is easily discernible by clever people collating that information.