Be very scared…

… The Real, Terrifying Reason Why British Authorities Detained David Miranda — Bruce Schneier - The Atlantic. (Hat tip, Dave Lull.)

This leaves one last possible explanation -- those in power were angry and impulsively acted on that anger. They're lashing out: sending a message and demonstrating that they're not to be messed with -- that the normal rules of polite conduct don't apply to people who screw with them. That's probably the scariest explanation of all. Both the U.S. and U.K. intelligence apparatuses have enormous money and power, and they have already demonstrated that they are willing to ignore their own laws. Once they start wielding that power unthinkingly, it could get really bad for everyone.