Do past abuses of personal data point toward future abuses of NSA metadata collection?

Stephen Walt spotlights why we worry about metadata collection:

The real risk to our democracy is what this situation does to potential dissenters, whistle-blowers, investigative journalists, and anyone else who thinks that some aspect of government policy might be boneheaded, unethical, or maybe even illegal. If you are one of those people -- even on just a single issue -- and you decide to go public with your concerns, there's a possibility that someone who doesn't like what you are doing will decide to see what they can find out about you. It doesn't have to be the attorney general either; it might just be some anonymous midlevel bureaucrat or overly zealous defense contractor. Or maybe it will be someone who wants to suck up to their superiors by taking down a critic or who wants to have their own 15 minutes of fame. It really doesn't matter: Unless you've lived an absolutely pristine online and cellular life, you might wake up to discover that some regrettable moment from your past is suddenly being plastered all over the blogosphere or discussed in the New York Times. 

 In a way, though, Walt's evidence that we should worry cuts two ways: