Millions of emails and phone calls have been registered, in secret, by US intelligence agencies. It seems the US government is now keeping an eye on all of us - regardless of our citizenship. The backlash has been particularly fierce in the European Union. Its justice commissioner, Viviane Reding, is demanding explanations from the US Attorney General Eric Holder. So how will the US respond to these demands? Can the surveillance operations be stopped? And what exactly is at risk?