Indeed. Consider someone is planning on going to an Occupy Wall Street protest. Say that the government is monitoring that persons emails and finds that the person wrote to a fellow protester: "man, fuck corporations, I can't wait to try and bring them down on xday." Now the people reading that private email decide that this message constitutes enough of a threat to act on. They send the police over to that guy's place on the day of the protest and have the police detain him for the rest of the day. They let him go once the protests wind down without incident.
Now I don't think anyone actually committed a crime in that scenario, but it is easy to see how such powers could be used to seriously hinder the democratic process.
Now I don't think anyone actually committed a crime in that scenario, but it is easy to see how such powers could be used to seriously hinder the democratic process.