The focus on content over meta-data is a red-herring. What you say during the phone call is just that...something you say. The meta-data shows what you do.

A person browses the web at a doctor's office. Forty-five minutes later, that person calls their spouse, then an oncologist. A few days later, their spouse checks email from the oncologists office. An hour later a call is made to a diagnostic center by the first person. The next day, they call their mother and a surgeon. [see interview with Susan Landau: http://www.democracynow.org/2013/6/12/more_intrusive_than_ea... ]

The conclusions which can be drawn from that meta-data are far more solid than can be drawn from listening in to any or all of the phone calls.

Your phone calls don't show what time you get up in the morning, or when you get to work or walk the dog to the park. The meta-data does.

The focus on the content of calls is 50 years out of date. The meta-data show the best time to burgle your house or fake your identity online. They show where you go and who you associate with. There's no need to know what you said.