The difference, for me anyhow, is I understand a private corp's motivation for tracking my every data point: money. Simple.
What a government's intentions might be for it seems hazier. Why, exactly, do they want it? Sure, they can trot out the national security routine to get started, but policies and power structures change every few years, and there's no telling how the next group will use (or abuse) that information once the precedent is set.
Somehow, the thought of, "Oh, they just want to make money," is more easily digested. Plus, I can immediately vote my opinion of their methods by not using their service(s). You can't opt out of the NSA's "service".
