The collection of all this mass data amounts to a government dossier on every individual who has a cell phone or a computer.
Here's the entire quote that puts it all in context:
It's the self-censorship, the hesitation, the fear that what you say or write or otherwise express today could be lurking somewhere on what Snowden referred to as your "permanent record" and come back to haunt you in the future. The collection of all this mass data amounts to a government dossier on every individual who has a cell phone or a computer. It's forcing journalists, teachers and political dissidents to be afraid of doing their jobs and exercising their democratic rights. It's making average citizens think twice about even doing silly things like search Amazon for pressure cookers or take a look at a controversial web-site.
And this is because no matter how much you may trust Barack Obama not to abuse that information it was only a few years ago that a man named Dick Cheney had access to it. Any of us can imagine what he might have done with it in the event of another major terrorist attack --- after all, the man hijacked the presidency and illegally ordered commercial planes to be shot down after the first one. You simply cannot rely on the good will of people like him to resist using that information for nefarious means in the future. And frankly, mere fact that the collection of all this information isn't giving results should make us all very leery about why they want it so badly.
The more power you give them the more they want, the more the bureaucracies need to justify themselves and ultimately the more tempting it will be to use the information for other purposes. It's just a very bad idea in every way.
So, let's get back to the 4th Amendment: specific warrants, for probable cause, issued by a judge to focus on a specific individual...not sweeping up massive amounts of data "just in case," just because we can.