If the corporations are storing the data already—for some business purpose—then the answer is easy: Only they should store it. If the corporations are not already storing the data, then—on balance—it's safer for the NSA to store the data. And in many cases, the right answer is for no one to store the data. It should be deleted because keeping it makes us all less secure.

Bruce Schneier's analysis of whether or not the NSA should store collected meta-data is correct and worth reading.