The Washington Post published an opinion piece that quotes the ACLU of Massachusetts (via John Gruber):

What does this rule change mean for you? In short, domestic law enforcement officials now have access to huge troves of American communications, obtained without warrants, that they can use to put people in cages. FBI agents don’t need to have any “national security” related reason to plug your name, email address, phone number, or other “selector” into the NSA’s gargantuan data trove. They can simply poke around in your private information in the course of totally routine investigations. And if they find something that suggests, say, involvement in illegal drug activity, they can send that information to local or state police. That means information the NSA collects for purposes of so-called “national security” will be used by police to lock up ordinary Americans for routine crimes.

Woah.