I can tell you why I object :
The fact that I do have nothing to hide does not mean you have permission to rifle through my life without a warrant (implying probably cause, which you don't have since I have nothing to hide).
The fact that so much data is gathered on everyone allows Big Data to find correlations that a human would take thousands of years to spot, meaning that advancements in data mining imply that all that data can conceivably find a way to implicate me personally in something I absolutely had no intention of participating in.
As in, if I somehow go every week at about the same time to the same place as an actual terrorist (think supermarket for food), my bloomin' so-called smartphone localizes me in the same general area at the same times, and I happen to be on camera with said terrorist (in the canned food aisle because he was asking about a specific price), I may get flagged as a potential contact, become a suspect and get my life invaded and overturned to find whatever excuse to jail me or at least ruin my future when I was just frakkin' shopping and so was he (because terrists eat too).